id stringlengths 9 13 | submitter stringlengths 1 64 ⌀ | authors stringlengths 5 22.9k | title stringlengths 4 245 | comments stringlengths 1 548 ⌀ | journal-ref stringlengths 4 362 ⌀ | doi stringlengths 12 82 ⌀ | report-no stringlengths 2 281 ⌀ | categories stringclasses 793 values | license stringclasses 9 values | orig_abstract stringlengths 24 1.95k | versions listlengths 1 30 | update_date stringlengths 10 10 | authors_parsed listlengths 1 1.74k | abstract stringlengths 21 1.95k |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1501.07243 | Walter Simon | Maria Eugenia Gabach Clement, Martin Reiris and Walter Simon | The area-angular momentum inequality for black holes in cosmological
spacetimes | 24p; minor corrections to v1 | null | null | null | gr-qc math.DG math.FA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | For a stable marginally outer trapped surface (MOTS) in an axially symmetric
spacetime with cosmological constant $\Lambda > 0$ and with matter satisfying
the dominant energy condition, we prove that the area $A$ and the angular
momentum $J$ satisfy the inequality $8\pi |J| \le A\sqrt{(1-\Lambda
A/4\pi)(1-\Lambda A/12\pi)}$ which is saturated precisely for the extreme
Kerr-deSitter family of metrics. This result entails a universal upper bound
$|J| \le J_{\max} \approx 0.17/\Lambda$ for such MOTS, which is saturated for
one particular extreme configuration. Our result sharpens the inequality $8\pi
|J| \le A$, [7,14] and we follow the overall strategy of its proof in the sense
that we estimate the area from below in terms of the energy corresponding to a
"mass functional", which is basically a suitably regularised harmonic map
$\mathbb{S}^2 \rightarrow \mathbb{H}^2 $. However, in the cosmological case
this mass functional acquires an additional potential term which itself depends
on the area. To estimate the corresponding energy in terms of the angular
momentum and the cosmological constant we use a subtle scaling argument, a
generalised "Carter-identity", and various techniques from variational
calculus, including the mountain pass theorem.
| [
{
"created": "Wed, 28 Jan 2015 19:12:51 GMT",
"version": "v1"
},
{
"created": "Mon, 2 Feb 2015 15:22:28 GMT",
"version": "v2"
}
] | 2015-02-12 | [
[
"Clement",
"Maria Eugenia Gabach",
""
],
[
"Reiris",
"Martin",
""
],
[
"Simon",
"Walter",
""
]
] | For a stable marginally outer trapped surface (MOTS) in an axially symmetric spacetime with cosmological constant $\Lambda > 0$ and with matter satisfying the dominant energy condition, we prove that the area $A$ and the angular momentum $J$ satisfy the inequality $8\pi |J| \le A\sqrt{(1-\Lambda A/4\pi)(1-\Lambda A/12\pi)}$ which is saturated precisely for the extreme Kerr-deSitter family of metrics. This result entails a universal upper bound $|J| \le J_{\max} \approx 0.17/\Lambda$ for such MOTS, which is saturated for one particular extreme configuration. Our result sharpens the inequality $8\pi |J| \le A$, [7,14] and we follow the overall strategy of its proof in the sense that we estimate the area from below in terms of the energy corresponding to a "mass functional", which is basically a suitably regularised harmonic map $\mathbb{S}^2 \rightarrow \mathbb{H}^2 $. However, in the cosmological case this mass functional acquires an additional potential term which itself depends on the area. To estimate the corresponding energy in terms of the angular momentum and the cosmological constant we use a subtle scaling argument, a generalised "Carter-identity", and various techniques from variational calculus, including the mountain pass theorem. |
2101.00493 | Jarmo M\"akel\"a Dr. | Jarmo M\"akel\"a | Brown-York Energy in Spacetimes with Horizon | 5 pages, no figures. Accepted for publication in the Physical Review
D | null | 10.1103/PhysRevD.103.026002 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | We obtain a simple relationship between the change in the Brown-York energy
inside of a closed two-surface just outside of a horizon of spacetime, and the
change in the area of that two-surface.
| [
{
"created": "Sat, 2 Jan 2021 18:41:26 GMT",
"version": "v1"
}
] | 2021-02-03 | [
[
"Mäkelä",
"Jarmo",
""
]
] | We obtain a simple relationship between the change in the Brown-York energy inside of a closed two-surface just outside of a horizon of spacetime, and the change in the area of that two-surface. |
1511.08835 | Miguel Sabido | M. Sabido and C. Yee-Romero | Deformed Phase Space Kaluza-Klein cosmology and late time acceleration | 5 pages, 2 figures, RevTeX 4.1 | null | 10.1016/j.physletb.2016.03.036 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The effects of phase space deformations on Kalutza-Klein cosmology are
studied. The deformation is introduced by modifying the symplectic structure of
the minisuperspace variables. In the deformed model, we find an accelerating
scale factor and therefore infer the existence of an effective cosmological
constant from the phase space deformation parameter $\beta$.
| [
{
"created": "Fri, 27 Nov 2015 21:59:06 GMT",
"version": "v1"
}
] | 2016-03-30 | [
[
"Sabido",
"M.",
""
],
[
"Yee-Romero",
"C.",
""
]
] | The effects of phase space deformations on Kalutza-Klein cosmology are studied. The deformation is introduced by modifying the symplectic structure of the minisuperspace variables. In the deformed model, we find an accelerating scale factor and therefore infer the existence of an effective cosmological constant from the phase space deformation parameter $\beta$. |
2012.08352 | Shahar Hod | Shahar Hod | Further evidence for the non-existence of a unified hoop conjecture | 11 pages | The European Physical Journal C 80, 982 (2020) | 10.1140/epjc/s10052-020-08558-8 | null | gr-qc astro-ph.HE hep-th | http://creativecommons.org/licenses/by/4.0/ | The hoop conjecture, introduced by Thorne almost five decades ago, asserts
that black holes are characterized by the mass-to-circumference relation $4\pi
{\cal M}/{\cal C}\geq1$, whereas horizonless compact objects are characterized
by the opposite inequality $4\pi {\cal M}/{\cal C}<1$ (here ${\cal C}$ is the
circumference of the smallest ring that can engulf the self-gravitating compact
object in all azimuthal directions). It has recently been proved that a
necessary condition for the validity of this conjecture in horizonless
spacetimes of spatially regular charged compact objects is that the mass ${\cal
M}$ be interpreted as the mass contained within the engulfing sphere (and not
as the asymptotically measured total ADM mass). In the present paper we raise
the following physically intriguing question: Is it possible to formulate a
unified version of the hoop conjecture which is valid for both black holes and
horizonless compact objects? In order to address this important question, we
analyze the behavior of the mass-to-circumference ratio of Kerr-Newman black
holes. We explicitly prove that if the mass ${\cal M}$ in the hoop relation is
interpreted as the quasilocal Einstein-Landau-Lifshitz-Papapetrou and Weinberg
mass contained within the black-hole horizon, then these charged and spinning
black holes are characterized by the sub-critical mass-to-circumference ratio
$4\pi {\cal M}/{\cal C}<1$. Our results provide evidence for the non-existence
of a unified version of the hoop conjecture which is valid for both black-hole
spacetimes and spatially regular horizonless compact objects.
| [
{
"created": "Tue, 15 Dec 2020 15:12:42 GMT",
"version": "v1"
}
] | 2020-12-23 | [
[
"Hod",
"Shahar",
""
]
] | The hoop conjecture, introduced by Thorne almost five decades ago, asserts that black holes are characterized by the mass-to-circumference relation $4\pi {\cal M}/{\cal C}\geq1$, whereas horizonless compact objects are characterized by the opposite inequality $4\pi {\cal M}/{\cal C}<1$ (here ${\cal C}$ is the circumference of the smallest ring that can engulf the self-gravitating compact object in all azimuthal directions). It has recently been proved that a necessary condition for the validity of this conjecture in horizonless spacetimes of spatially regular charged compact objects is that the mass ${\cal M}$ be interpreted as the mass contained within the engulfing sphere (and not as the asymptotically measured total ADM mass). In the present paper we raise the following physically intriguing question: Is it possible to formulate a unified version of the hoop conjecture which is valid for both black holes and horizonless compact objects? In order to address this important question, we analyze the behavior of the mass-to-circumference ratio of Kerr-Newman black holes. We explicitly prove that if the mass ${\cal M}$ in the hoop relation is interpreted as the quasilocal Einstein-Landau-Lifshitz-Papapetrou and Weinberg mass contained within the black-hole horizon, then these charged and spinning black holes are characterized by the sub-critical mass-to-circumference ratio $4\pi {\cal M}/{\cal C}<1$. Our results provide evidence for the non-existence of a unified version of the hoop conjecture which is valid for both black-hole spacetimes and spatially regular horizonless compact objects. |
2108.09930 | Farook Rahaman | Farook Rahaman, Ksh. Newton Singh, Rajibul Shaikh, Tuhina Manna and
Somi Aktar | Shadows of Lorentzian traversable wormholes | 12 pages, 7 figures. published in Class.Quan.Grav | Class. Quantum Grav. 38 (2021) 215007 | 10.1088/1361-6382/ac213b | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | The prospect of identifying wormholes by investigating the shadows of
wormholes constitute a foremost source of insight into the evolution of compact
objects and it is one of the essential problems in contemporary astrophysics.
The nature of the compact objects (wormholes) plays a crucial role on shadow
effect, which actually arises during the strong gravitational lensing. Current
Event Horizon Telescope observations have inspired scientists to study and to
construct the shadow images of the wormholes. In this work, we explore the
shadow cast by a certain class of rotating wormhole. To search this, we first
compose the null geodesics and study the effects of the parameters on the
photon orbit. We have exposed the form and size of the wormhole shadow and have
found that it is slanted as well as can be altered depending on the different
parameters present in the wormhole spacetime. We also constrain the size and
the spin of the wormhole using the results from M87* observation, by
investigating the average diameter of the wormhole as well as deviation from
circularity with respect to the wormhole throat size. In a future observation,
this type of study may help to indicate the presence of a wormhole in a
galactic region.
| [
{
"created": "Mon, 23 Aug 2021 04:43:26 GMT",
"version": "v1"
},
{
"created": "Sun, 31 Oct 2021 17:05:04 GMT",
"version": "v2"
}
] | 2021-11-02 | [
[
"Rahaman",
"Farook",
""
],
[
"Singh",
"Ksh. Newton",
""
],
[
"Shaikh",
"Rajibul",
""
],
[
"Manna",
"Tuhina",
""
],
[
"Aktar",
"Somi",
""
]
] | The prospect of identifying wormholes by investigating the shadows of wormholes constitute a foremost source of insight into the evolution of compact objects and it is one of the essential problems in contemporary astrophysics. The nature of the compact objects (wormholes) plays a crucial role on shadow effect, which actually arises during the strong gravitational lensing. Current Event Horizon Telescope observations have inspired scientists to study and to construct the shadow images of the wormholes. In this work, we explore the shadow cast by a certain class of rotating wormhole. To search this, we first compose the null geodesics and study the effects of the parameters on the photon orbit. We have exposed the form and size of the wormhole shadow and have found that it is slanted as well as can be altered depending on the different parameters present in the wormhole spacetime. We also constrain the size and the spin of the wormhole using the results from M87* observation, by investigating the average diameter of the wormhole as well as deviation from circularity with respect to the wormhole throat size. In a future observation, this type of study may help to indicate the presence of a wormhole in a galactic region. |
2010.09224 | Jia-Xi Feng | Jia-Xi Feng, Fu-Wen Shu and Anzhong Wang | Rotations of the polarization of a gravitational wave propagating in
Universe | 35 pages, 9 figures,improvements to presentation, references added,
and new content added in appendix to comment about gauge invariance,
published version in Nuclear Physics B | Nuclear Physics B (2021) | 10.1016/j.nuclphysb.2021.115578 | null | gr-qc astro-ph.CO astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we study the polarization of a gravitational wave (GW) emitted
by an astrophysical source at a cosmic distance propagating through the
Friedmann-Lema\^itre-Robertson-Walk universe. By considering the null geodesic
deviations, we first provide a definition of the polarization of the GW in
terms of the Weyl scalars with respect to a parallelly-transported frame along
the null geodesics, and then show explicitly that, due to different effects of
the expansion of the universe on the two polarization modes, the so-called "+"
and "$\times$" modes, the polarization angle of the GW changes generically,
when it is propagating through the curved background. By direct computations of
the polarization angle, we show that different epochs, radiation-, matter- and
$\Lambda$-dominated, have different effects on the polarization. In particular,
for a GW emitted by a binary system, we find explicitly the relation between
the change of the polarization angle $|\Delta \varphi|$ and the redshift $z_s$
of the source in different epochs. In the $\Lambda$CDM model, we find that the
order of $|\Delta \varphi|{\eta_0 F}$ is typically $O(10^{-3})$ to $O(10^3)$,
depending on the values of $z_s$, where $\eta_0$ is the (comoving) time of the
current universe, and
$F\equiv\Big(\frac{5}{256}\frac{1}{\tau_{obs}}\Big)^{3/8}\left(G_NM_c\right)^{-5/8}$
with $\tau_{obs}$ and $M_c$ being, respectively, the time to coalescence in the
observer's frame and the chirp mass of the binary system.
| [
{
"created": "Mon, 19 Oct 2020 04:55:41 GMT",
"version": "v1"
},
{
"created": "Fri, 22 Oct 2021 02:54:31 GMT",
"version": "v2"
}
] | 2021-10-25 | [
[
"Feng",
"Jia-Xi",
""
],
[
"Shu",
"Fu-Wen",
""
],
[
"Wang",
"Anzhong",
""
]
] | In this paper, we study the polarization of a gravitational wave (GW) emitted by an astrophysical source at a cosmic distance propagating through the Friedmann-Lema\^itre-Robertson-Walk universe. By considering the null geodesic deviations, we first provide a definition of the polarization of the GW in terms of the Weyl scalars with respect to a parallelly-transported frame along the null geodesics, and then show explicitly that, due to different effects of the expansion of the universe on the two polarization modes, the so-called "+" and "$\times$" modes, the polarization angle of the GW changes generically, when it is propagating through the curved background. By direct computations of the polarization angle, we show that different epochs, radiation-, matter- and $\Lambda$-dominated, have different effects on the polarization. In particular, for a GW emitted by a binary system, we find explicitly the relation between the change of the polarization angle $|\Delta \varphi|$ and the redshift $z_s$ of the source in different epochs. In the $\Lambda$CDM model, we find that the order of $|\Delta \varphi|{\eta_0 F}$ is typically $O(10^{-3})$ to $O(10^3)$, depending on the values of $z_s$, where $\eta_0$ is the (comoving) time of the current universe, and $F\equiv\Big(\frac{5}{256}\frac{1}{\tau_{obs}}\Big)^{3/8}\left(G_NM_c\right)^{-5/8}$ with $\tau_{obs}$ and $M_c$ being, respectively, the time to coalescence in the observer's frame and the chirp mass of the binary system. |
1310.4771 | George F. R. Ellis | George F R Ellis | Astrophysical black holes may radiate, but they do not evaporate | 56 pages, 10 Figures, 4 Tables. Errors corrected, new references
added, new section and appendix. Basic argument and outcome unchanged | null | null | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper argues that the effect of Hawking radiation on an astrophysical
black hole situated in a realistic cosmological context is not total
evaporation of the black hole; rather there will always be a remnant mass. The
key point is that the locus of emission of Hawking radiation is not the
globally defined event horizon. Rather the emission domain lies just outside a
timelike Marginal Outer Trapped Surface that is locally defined. The emission
domain is mainly located inside the event horizon. A spacelike singularity
forms behind the event horizon, and most of the Hawking radiation ends up at
this singularity rather than at infinity. Whether any Hawking radiation reaches
infinity depends on the relation between the emission domain and the event
horizon. From the outside view, even if radiation is seen as always being
emitted, the black hole never evaporates away, rather its mass and entropy
asymptote to finite non-zero limits, and the event horizon always acts as a
sink for matter and information. From an inside view, the matter and
information disappear into the singularity, which is the boundary of spacetime.
The argument is based on the nature of the processes at work plus a careful
delineation of the relevant causal domains; in order to confirm this model and
determine details of the outcome, detailed calculations of the expectation
value of the stress-energy-momentum tensor are needed to determine back
reaction effects.
| [
{
"created": "Thu, 17 Oct 2013 16:56:53 GMT",
"version": "v1"
},
{
"created": "Sun, 20 Oct 2013 06:05:14 GMT",
"version": "v2"
}
] | 2013-10-22 | [
[
"Ellis",
"George F R",
""
]
] | This paper argues that the effect of Hawking radiation on an astrophysical black hole situated in a realistic cosmological context is not total evaporation of the black hole; rather there will always be a remnant mass. The key point is that the locus of emission of Hawking radiation is not the globally defined event horizon. Rather the emission domain lies just outside a timelike Marginal Outer Trapped Surface that is locally defined. The emission domain is mainly located inside the event horizon. A spacelike singularity forms behind the event horizon, and most of the Hawking radiation ends up at this singularity rather than at infinity. Whether any Hawking radiation reaches infinity depends on the relation between the emission domain and the event horizon. From the outside view, even if radiation is seen as always being emitted, the black hole never evaporates away, rather its mass and entropy asymptote to finite non-zero limits, and the event horizon always acts as a sink for matter and information. From an inside view, the matter and information disappear into the singularity, which is the boundary of spacetime. The argument is based on the nature of the processes at work plus a careful delineation of the relevant causal domains; in order to confirm this model and determine details of the outcome, detailed calculations of the expectation value of the stress-energy-momentum tensor are needed to determine back reaction effects. |
1003.3421 | Daniel Vanzella | William C. C. Lima and Daniel A. T. Vanzella | Gravity-induced vacuum dominance | To appear in Phys. Rev. Lett. | Phys.Rev.Lett.104:161102,2010 | 10.1103/PhysRevLett.104.161102 | null | gr-qc astro-ph.SR hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It has been widely believed that, except in very extreme situations, the
influence of gravity on quantum fields should amount to just small,
sub-dominant contributions. This view seemed to be endorsed by the seminal
results obtained over the last decades in the context of renormalization of
quantum fields in curved spacetimes. Here, however, we argue that this belief
is false by showing that there exist well-behaved spacetime evolutions where
the vacuum energy density of free quantum fields is forced, by the very same
background spacetime, to become dominant over any classical energy-density
component. This semiclassical gravity effect finds its roots in the infrared
behavior of fields on curved spacetimes. By estimating the time scale for the
vacuum energy density to become dominant, and therefore for backreaction on the
background spacetime to become important, we argue that this vacuum dominance
may bear unexpected astrophysical and cosmological implications.
| [
{
"created": "Wed, 17 Mar 2010 18:10:17 GMT",
"version": "v1"
}
] | 2010-05-12 | [
[
"Lima",
"William C. C.",
""
],
[
"Vanzella",
"Daniel A. T.",
""
]
] | It has been widely believed that, except in very extreme situations, the influence of gravity on quantum fields should amount to just small, sub-dominant contributions. This view seemed to be endorsed by the seminal results obtained over the last decades in the context of renormalization of quantum fields in curved spacetimes. Here, however, we argue that this belief is false by showing that there exist well-behaved spacetime evolutions where the vacuum energy density of free quantum fields is forced, by the very same background spacetime, to become dominant over any classical energy-density component. This semiclassical gravity effect finds its roots in the infrared behavior of fields on curved spacetimes. By estimating the time scale for the vacuum energy density to become dominant, and therefore for backreaction on the background spacetime to become important, we argue that this vacuum dominance may bear unexpected astrophysical and cosmological implications. |
2111.03277 | Banibrata Mukhopadhyay | Banibrata Mukhopadhyay, Tanuman Ghosh, Soumya Kanti Ganguly | Gravitational geometric phase | 10 pages; based on the talk given in the 16th Marcel Grossmann
Meeting (MG16) held online during July 5-10, 2021; to appear in the
proceeding of MG16 | null | null | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We show that spinors propagating in curved gravitational background acquire
an interaction with spacetime curvature, which leads to a quantum mechanical
geometric effect. This is similar to what happens in the case of magnetic
fields, known as Pancharatnam-Berry phase. As the magnetic and gravitational
fields have certain similar properties, e.g. both contribute to curvature, this
result is not difficult to understand. Interestingly, while spacetime around a
rotating black hole offers Aharonov-Bohm and Pancharatnam-Berry both kinds of
geometric effect, a static spacetime offers only the latter. In the bath of
primordial black holes, such gravity induced effects could easily be measured
due to their smaller radius.
| [
{
"created": "Fri, 5 Nov 2021 05:44:09 GMT",
"version": "v1"
}
] | 2021-11-09 | [
[
"Mukhopadhyay",
"Banibrata",
""
],
[
"Ghosh",
"Tanuman",
""
],
[
"Ganguly",
"Soumya Kanti",
""
]
] | We show that spinors propagating in curved gravitational background acquire an interaction with spacetime curvature, which leads to a quantum mechanical geometric effect. This is similar to what happens in the case of magnetic fields, known as Pancharatnam-Berry phase. As the magnetic and gravitational fields have certain similar properties, e.g. both contribute to curvature, this result is not difficult to understand. Interestingly, while spacetime around a rotating black hole offers Aharonov-Bohm and Pancharatnam-Berry both kinds of geometric effect, a static spacetime offers only the latter. In the bath of primordial black holes, such gravity induced effects could easily be measured due to their smaller radius. |
gr-qc/0603012 | Jannie Leach | Jannie A Leach, Sante Carloni and Peter K S Dunsby | Shear dynamics in Bianchi I cosmologies with R^n-gravity | 25 pages LaTeX, 6 figures. Revised to match the final version
accepted for publication in CQG | Class.Quant.Grav.23:4915-4937,2006 | 10.1088/0264-9381/23/15/011 | null | gr-qc astro-ph hep-th | null | We give the equations governing the shear evolution in Bianchi spacetimes for
general f(R)-theories of gravity. We consider the case of R^n-gravity and
perform a detailed analysis of the dynamics in Bianchi I cosmologies which
exhibit local rotational symmetry. We find exact solutions and study their
behaviour and stability in terms of the values of the parameter n. In
particular, we found a set of cosmic histories in which the universe is
initially isotropic, then develops shear anisotropies which approaches a
constant value.
| [
{
"created": "Mon, 6 Mar 2006 16:22:50 GMT",
"version": "v1"
},
{
"created": "Fri, 23 Jun 2006 09:58:26 GMT",
"version": "v2"
}
] | 2010-11-05 | [
[
"Leach",
"Jannie A",
""
],
[
"Carloni",
"Sante",
""
],
[
"Dunsby",
"Peter K S",
""
]
] | We give the equations governing the shear evolution in Bianchi spacetimes for general f(R)-theories of gravity. We consider the case of R^n-gravity and perform a detailed analysis of the dynamics in Bianchi I cosmologies which exhibit local rotational symmetry. We find exact solutions and study their behaviour and stability in terms of the values of the parameter n. In particular, we found a set of cosmic histories in which the universe is initially isotropic, then develops shear anisotropies which approaches a constant value. |
gr-qc/0611143 | Katanaev | G. de Berredo-Peixoto, M. O. Katanaev | Inside the BTZ black hole | 24 pages, 8 figures | Phys.Rev.D75:024004,2007 | 10.1103/PhysRevD.75.024004 | null | gr-qc | null | We consider static circularly symmetric solution of three-dimensional
Einstein's equations with negative cosmological constant (the BTZ black hole).
The case of zero cosmological constant corresponding to the interior region of
a black hole is analyzed in detail. We prove that the maximally extended BTZ
solution with zero cosmological constant coincides with flat three-dimensional
Minkowskian space-time without any singularity and horizons. The Euclidean
version of this solution is shown to have physical interpretation in the
geometric theory of defects in solids describing combined wedge and screw
dislocations.
| [
{
"created": "Mon, 27 Nov 2006 19:31:30 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"de Berredo-Peixoto",
"G.",
""
],
[
"Katanaev",
"M. O.",
""
]
] | We consider static circularly symmetric solution of three-dimensional Einstein's equations with negative cosmological constant (the BTZ black hole). The case of zero cosmological constant corresponding to the interior region of a black hole is analyzed in detail. We prove that the maximally extended BTZ solution with zero cosmological constant coincides with flat three-dimensional Minkowskian space-time without any singularity and horizons. The Euclidean version of this solution is shown to have physical interpretation in the geometric theory of defects in solids describing combined wedge and screw dislocations. |
2105.00066 | Dong-han Yeom | Dong-han Yeom | Speculation about the black hole final state: resolving singularity by
quantum gravity | 4 pages, 1 figure; Proceedings of Beyond Standard Model: From Theory
to Experiment. Talk on March 29, 2021, Giza, Egypt | null | 10.31526/ACP.BSM-2021.37 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | The interior of the black hole can be described by anisotropic cosmology. By
quantizing the metric function, we can obtain the Wheeler-DeWitt equation for
inside the horizon. In order to interpret the wave function consistently, one
needs to impose a boundary condition. In this paper, we introduce a
prescription for the Euclidean analytic continuation inside the horizon and the
corresponding wave function solution.
| [
{
"created": "Fri, 30 Apr 2021 20:02:04 GMT",
"version": "v1"
}
] | 2022-09-08 | [
[
"Yeom",
"Dong-han",
""
]
] | The interior of the black hole can be described by anisotropic cosmology. By quantizing the metric function, we can obtain the Wheeler-DeWitt equation for inside the horizon. In order to interpret the wave function consistently, one needs to impose a boundary condition. In this paper, we introduce a prescription for the Euclidean analytic continuation inside the horizon and the corresponding wave function solution. |
0709.0732 | David Wiltshire | David L. Wiltshire | Exact solution to the averaging problem in cosmology | 4 pages; v2 references added, to appear in Phys. Rev. Letters | Phys.Rev.Lett.99:251101,2007 | 10.1103/PhysRevLett.99.251101 | null | gr-qc astro-ph hep-ph hep-th | null | The exact solution of a two-scale Buchert average of the Einstein equations
is derived for an inhomogeneous universe which represents a close approximation
to the observed universe. The two scales represent voids, and the bubble walls
surrounding them within which clusters of galaxies are located. As described
elsewhere [gr-qc/0702082], apparent cosmic acceleration can be recognised as a
consequence of quasilocal gravitational energy gradients between observers in
bound systems and the volume average position in freely expanding space. With
this interpretation, the new solution presented here replaces the Friedmann
solutions, in representing the average evolution of a matter-dominated universe
without exotic dark energy, while being observationally viable.
| [
{
"created": "Thu, 6 Sep 2007 11:57:39 GMT",
"version": "v1"
},
{
"created": "Thu, 1 Nov 2007 05:28:14 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Wiltshire",
"David L.",
""
]
] | The exact solution of a two-scale Buchert average of the Einstein equations is derived for an inhomogeneous universe which represents a close approximation to the observed universe. The two scales represent voids, and the bubble walls surrounding them within which clusters of galaxies are located. As described elsewhere [gr-qc/0702082], apparent cosmic acceleration can be recognised as a consequence of quasilocal gravitational energy gradients between observers in bound systems and the volume average position in freely expanding space. With this interpretation, the new solution presented here replaces the Friedmann solutions, in representing the average evolution of a matter-dominated universe without exotic dark energy, while being observationally viable. |
1406.7587 | Kent Yagi | Kent Yagi, Leo C. Stein, George Pappas, Nicolas Yunes, Theocharis A.
Apostolatos | Why I-Love-Q | 23 pages, 22 figures; matches version appearing in PRD | Phys. Rev. D 90, 063010 (2014) | 10.1103/PhysRevD.90.063010 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Black holes are said to have no hair because all of their multipole moments
can be expressed in terms of just their mass, charge and spin angular momentum.
The recent discovery of approximately equation-of-state-independent relations
among certain multipole moments in neutron stars suggests that they are also
approximately bald. We here explore the yet unknown origin for this
universality. First, we investigate which region of the neutron star's interior
and of the equation of state is most responsible for the universality. We find
that the universal relation between the moment of inertia and the quadrupole
moment is dominated by the star's outer-core, a shell of width (50-95)% of the
total radius, which corresponds to the density range
$(10^{14}$-$10^{15})$g/cm$^3$. Second, we study the impact on the universality
of approximating stellar isodensity contours as self-similar ellipsoids. An
analytical calculation in the Newtonian limit reveals that the shape of the
ellipsoids does not affect the universal relations, but relaxing the
self-similarity assumption can completely destroy it. Third, we investigate the
eccentricity profiles of rotating relativistic stars and find that the
ellipticity is roughly constant, with variations of roughly (20-30)% in the
region that matters to the universal relations. Fourth, we repeat the above
analysis for non-compact, regular stars and find that the ellipticity is not
constant, with variations that easily exceed 100% and universality is lost.
These findings suggest that universality arises as an emergent approximate
symmetry: as one flows in the stellar-structure phase space from non-compact
star region to the relativistic star region, the eccentricity variation inside
stars decreases, leading to approximate self-similarity in their isodensity
contours, which then leads to the universal behavior observed in their exterior
multipole moments.
| [
{
"created": "Mon, 30 Jun 2014 02:54:43 GMT",
"version": "v1"
},
{
"created": "Mon, 8 Sep 2014 17:49:24 GMT",
"version": "v2"
}
] | 2014-09-25 | [
[
"Yagi",
"Kent",
""
],
[
"Stein",
"Leo C.",
""
],
[
"Pappas",
"George",
""
],
[
"Yunes",
"Nicolas",
""
],
[
"Apostolatos",
"Theocharis A.",
""
]
] | Black holes are said to have no hair because all of their multipole moments can be expressed in terms of just their mass, charge and spin angular momentum. The recent discovery of approximately equation-of-state-independent relations among certain multipole moments in neutron stars suggests that they are also approximately bald. We here explore the yet unknown origin for this universality. First, we investigate which region of the neutron star's interior and of the equation of state is most responsible for the universality. We find that the universal relation between the moment of inertia and the quadrupole moment is dominated by the star's outer-core, a shell of width (50-95)% of the total radius, which corresponds to the density range $(10^{14}$-$10^{15})$g/cm$^3$. Second, we study the impact on the universality of approximating stellar isodensity contours as self-similar ellipsoids. An analytical calculation in the Newtonian limit reveals that the shape of the ellipsoids does not affect the universal relations, but relaxing the self-similarity assumption can completely destroy it. Third, we investigate the eccentricity profiles of rotating relativistic stars and find that the ellipticity is roughly constant, with variations of roughly (20-30)% in the region that matters to the universal relations. Fourth, we repeat the above analysis for non-compact, regular stars and find that the ellipticity is not constant, with variations that easily exceed 100% and universality is lost. These findings suggest that universality arises as an emergent approximate symmetry: as one flows in the stellar-structure phase space from non-compact star region to the relativistic star region, the eccentricity variation inside stars decreases, leading to approximate self-similarity in their isodensity contours, which then leads to the universal behavior observed in their exterior multipole moments. |
1809.09125 | Vijay Varma | Vijay Varma, Davide Gerosa, Leo C. Stein, Fran\c{c}ois H\'ebert, and
Hao Zhang | High-accuracy mass, spin, and recoil predictions of generic black-hole
merger remnants | 6+5 pages. Matches PRL version. Python implementation available at
https://pypi.org/project/surfinBH/ | Phys. Rev. Lett. 122, 011101 (2019) | 10.1103/PhysRevLett.122.011101 | null | gr-qc astro-ph.HE | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present accurate fits for the remnant properties of generically precessing
binary black holes, trained on large banks of numerical-relativity simulations.
We use Gaussian process regression to interpolate the remnant mass, spin, and
recoil velocity in the 7-dimensional parameter space of precessing black-hole
binaries with mass ratios $q\leq2$, and spin magnitudes $\chi_1,\chi_2\leq0.8$.
For precessing systems, our errors in estimating the remnant mass, spin
magnitude, and kick magnitude are lower than those of existing fitting formulae
by at least an order of magnitude (improvement is also reported in the
extrapolated region at high mass ratios and spins). In addition, we also model
the remnant spin and kick directions. Being trained directly on precessing
simulations, our fits are free from ambiguities regarding the initial frequency
at which precessing quantities are defined. We also construct a model for
remnant properties of aligned-spin systems with mass ratios $q\leq8$, and spin
magnitudes $\chi_1,\chi_2\leq0.8$. As a byproduct, we also provide error
estimates for all fitted quantities, which can be consistently incorporated
into current and future gravitational-wave parameter-estimation analyses. Our
model(s) are made publicly available through a fast and easy-to-use Python
module called surfinBH.
| [
{
"created": "Mon, 24 Sep 2018 18:00:21 GMT",
"version": "v1"
},
{
"created": "Thu, 10 Jan 2019 17:04:06 GMT",
"version": "v2"
}
] | 2019-01-16 | [
[
"Varma",
"Vijay",
""
],
[
"Gerosa",
"Davide",
""
],
[
"Stein",
"Leo C.",
""
],
[
"Hébert",
"François",
""
],
[
"Zhang",
"Hao",
""
]
] | We present accurate fits for the remnant properties of generically precessing binary black holes, trained on large banks of numerical-relativity simulations. We use Gaussian process regression to interpolate the remnant mass, spin, and recoil velocity in the 7-dimensional parameter space of precessing black-hole binaries with mass ratios $q\leq2$, and spin magnitudes $\chi_1,\chi_2\leq0.8$. For precessing systems, our errors in estimating the remnant mass, spin magnitude, and kick magnitude are lower than those of existing fitting formulae by at least an order of magnitude (improvement is also reported in the extrapolated region at high mass ratios and spins). In addition, we also model the remnant spin and kick directions. Being trained directly on precessing simulations, our fits are free from ambiguities regarding the initial frequency at which precessing quantities are defined. We also construct a model for remnant properties of aligned-spin systems with mass ratios $q\leq8$, and spin magnitudes $\chi_1,\chi_2\leq0.8$. As a byproduct, we also provide error estimates for all fitted quantities, which can be consistently incorporated into current and future gravitational-wave parameter-estimation analyses. Our model(s) are made publicly available through a fast and easy-to-use Python module called surfinBH. |
0801.2919 | Yuri Bonder | Y. Bonder | A Lorentz Invariant Phenomenological Model of Quantum Gravity | 7 pages. Talk presented at "From Quantum to Emergent Gravity: Theory
and Phenomenology," June 2007, Trieste, Italy | null | null | null | gr-qc | null | We consider a model of Quantum Gravity phenomenology, based on the idea that
space-time may have some unknown granular structure that respects the Lorentz
symmetry. The proposal involves non-trivial couplings of curvature to matter
fields and leads to a well defined phenomenology. In this manuscript, a brief
description of the model is presented together with some results obtained using
linearized gravity and the Newtonian limit, which could be useful when
comparing with real experiments.
| [
{
"created": "Fri, 18 Jan 2008 16:04:15 GMT",
"version": "v1"
}
] | 2008-01-21 | [
[
"Bonder",
"Y.",
""
]
] | We consider a model of Quantum Gravity phenomenology, based on the idea that space-time may have some unknown granular structure that respects the Lorentz symmetry. The proposal involves non-trivial couplings of curvature to matter fields and leads to a well defined phenomenology. In this manuscript, a brief description of the model is presented together with some results obtained using linearized gravity and the Newtonian limit, which could be useful when comparing with real experiments. |
2003.07431 | Israel Quiros | Israel Quiros, Tame Gonzalez, Roberto De Arcia, Ricardo
Garc\'ia-Salcedo, Ulises Nucamendi, Joel F. Saavedra | Inflationary equilibrium configurations of scalar-tensor theories of
gravity | 30 pages, 6 figures (12 eps files). Comments acknowledged. Version
accepted in PRD | Phys. Rev. D 101, 103518 (2020) | 10.1103/PhysRevD.101.103518 | null | gr-qc astro-ph.CO | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper we investigate the asymptotic dynamics of inflationary
cosmological models that are based in scalar-tensor theories of gravity. Our
main aim is to explore the global structure of the phase space in the framework
of single-field inflation models. For this purpose we make emphasis in the
adequate choice of the variables of the phase space. Our results indicate that,
although single-field inflation is generic in the sense that the corresponding
critical point in the phase space exists for a wide class of potentials, along
given phase space orbits -- representing potential cosmic histories -- the
occurrence of the inflationary stage is rather dependent on the initial
conditions. We have been able to give quantitative estimates of the relative
probability (RP) for initial conditions leading to slow-roll inflation. For the
non-minimal coupling model with the $\phi^2$-potential our rough estimates
yield to an almost vanishing relative probability: $10^{-13}\,\%\lesssim RP\ll
10^{-8}\,\%$. These bonds are greatly improved in the scalar-tensor models,
including the Brans-Dicke theory, where the relative probability $1\,\%\lesssim
RP\leq 100\,\%$. Hence slow-roll inflation is indeed a natural stage of the
cosmic expansion in Brans-Dicke models of inflation. It is confirmed as well
that the dynamics of vacuum Brans-Dicke theories with arbitrary potentials are
non-chaotic.
| [
{
"created": "Mon, 16 Mar 2020 20:28:31 GMT",
"version": "v1"
},
{
"created": "Fri, 24 Apr 2020 18:42:11 GMT",
"version": "v2"
}
] | 2020-05-20 | [
[
"Quiros",
"Israel",
""
],
[
"Gonzalez",
"Tame",
""
],
[
"De Arcia",
"Roberto",
""
],
[
"García-Salcedo",
"Ricardo",
""
],
[
"Nucamendi",
"Ulises",
""
],
[
"Saavedra",
"Joel F.",
""
]
] | In this paper we investigate the asymptotic dynamics of inflationary cosmological models that are based in scalar-tensor theories of gravity. Our main aim is to explore the global structure of the phase space in the framework of single-field inflation models. For this purpose we make emphasis in the adequate choice of the variables of the phase space. Our results indicate that, although single-field inflation is generic in the sense that the corresponding critical point in the phase space exists for a wide class of potentials, along given phase space orbits -- representing potential cosmic histories -- the occurrence of the inflationary stage is rather dependent on the initial conditions. We have been able to give quantitative estimates of the relative probability (RP) for initial conditions leading to slow-roll inflation. For the non-minimal coupling model with the $\phi^2$-potential our rough estimates yield to an almost vanishing relative probability: $10^{-13}\,\%\lesssim RP\ll 10^{-8}\,\%$. These bonds are greatly improved in the scalar-tensor models, including the Brans-Dicke theory, where the relative probability $1\,\%\lesssim RP\leq 100\,\%$. Hence slow-roll inflation is indeed a natural stage of the cosmic expansion in Brans-Dicke models of inflation. It is confirmed as well that the dynamics of vacuum Brans-Dicke theories with arbitrary potentials are non-chaotic. |
1504.02068 | Mehdi Assanioussi | Emanuele Alesci, Mehdi Assanioussi, Jerzy Lewandowski, Ilkka M\"akinen | Hamiltonian operator for loop quantum gravity coupled to a scalar field | Minor corrections implemented | Phys. Rev. D 91, 124067 (2015) | 10.1103/PhysRevD.91.124067 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present the construction of a physical Hamiltonian operator in the
deparametrized model of loop quantum gravity coupled to a free scalar field.
This construction is based on the use of the recently introduced curvature
operator, and on the idea of so-called "special loops". We discuss in detail
the regularization procedure and the assignment of the loops, along with the
properties of the resulting operator. We compute the action of the squared
Hamiltonian operator on spin network states, and close with some comments and
outlooks.
| [
{
"created": "Wed, 8 Apr 2015 18:28:28 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Jun 2015 15:08:35 GMT",
"version": "v2"
}
] | 2015-06-25 | [
[
"Alesci",
"Emanuele",
""
],
[
"Assanioussi",
"Mehdi",
""
],
[
"Lewandowski",
"Jerzy",
""
],
[
"Mäkinen",
"Ilkka",
""
]
] | We present the construction of a physical Hamiltonian operator in the deparametrized model of loop quantum gravity coupled to a free scalar field. This construction is based on the use of the recently introduced curvature operator, and on the idea of so-called "special loops". We discuss in detail the regularization procedure and the assignment of the loops, along with the properties of the resulting operator. We compute the action of the squared Hamiltonian operator on spin network states, and close with some comments and outlooks. |
1906.03131 | Luciano Petruzziello | Luca Buoninfante, Giuseppe Gaetano Luciano, Luciano Petruzziello and
Luca Smaldone | Neutrino oscillations in extended theories of gravity | null | Phys. Rev. D 101, 024016 (2020) | 10.1103/PhysRevD.101.024016 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study neutrino oscillations within the framework of extended theories of
gravity. Based on the covariant reformulation of Pontecorvo formalism, we
evaluate the oscillation probability of neutrinos propagating in static
spacetimes described by gravitational actions quadratic in the curvature
invariants. Calculations are carried out in the two-flavor approximation, for
oscillations both in vacuum and matter. It is shown that the neutrino phase is
sensitive to the violation of the strong equivalence principle. By way of
illustration, we specialize our analysis to various extended models of gravity
in order both to quantify such a violation and to understand how the
characteristic free parameters of these models affect the neutrino phase. The
possibility to fix new bounds on these parameters and to constrain extended
theories of gravity is finally discussed.
| [
{
"created": "Fri, 7 Jun 2019 14:34:58 GMT",
"version": "v1"
},
{
"created": "Wed, 15 Jan 2020 10:41:39 GMT",
"version": "v2"
}
] | 2020-01-22 | [
[
"Buoninfante",
"Luca",
""
],
[
"Luciano",
"Giuseppe Gaetano",
""
],
[
"Petruzziello",
"Luciano",
""
],
[
"Smaldone",
"Luca",
""
]
] | We study neutrino oscillations within the framework of extended theories of gravity. Based on the covariant reformulation of Pontecorvo formalism, we evaluate the oscillation probability of neutrinos propagating in static spacetimes described by gravitational actions quadratic in the curvature invariants. Calculations are carried out in the two-flavor approximation, for oscillations both in vacuum and matter. It is shown that the neutrino phase is sensitive to the violation of the strong equivalence principle. By way of illustration, we specialize our analysis to various extended models of gravity in order both to quantify such a violation and to understand how the characteristic free parameters of these models affect the neutrino phase. The possibility to fix new bounds on these parameters and to constrain extended theories of gravity is finally discussed. |
1201.1655 | Carlos Kozameh | Melina Bordcoch, Carlos Kozameh, Alejandra Rojas | NSF 2.0: A spin weight zero formulation of General Relativity | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a set of three PDEs for three real scalars that are equivalent to
the full Einstein equations without any symmetry assumptions. The main
variables in this formulation are null surfaces and a conformal factor.
Furthermore, for asymptotically flat spacetimes the free data (representing
gravitational radiation) enters as the source term in the resulting equations.
This could be important for an asymptotic quantization procedure.
| [
{
"created": "Sun, 8 Jan 2012 20:15:47 GMT",
"version": "v1"
},
{
"created": "Sat, 14 Jan 2012 15:26:21 GMT",
"version": "v2"
}
] | 2012-01-17 | [
[
"Bordcoch",
"Melina",
""
],
[
"Kozameh",
"Carlos",
""
],
[
"Rojas",
"Alejandra",
""
]
] | We present a set of three PDEs for three real scalars that are equivalent to the full Einstein equations without any symmetry assumptions. The main variables in this formulation are null surfaces and a conformal factor. Furthermore, for asymptotically flat spacetimes the free data (representing gravitational radiation) enters as the source term in the resulting equations. This could be important for an asymptotic quantization procedure. |
gr-qc/0407070 | Wojciech P. Tarkowski | Wojciech P. Tarkowski | Searching for a solution to the cosmological constant problem - a toy
model | 53 pages, 2 figures; published in 2001, a number of sentences added | Class.Quant.Grav.18:2359-2391,2001 | 10.1088/0264-9381/18/12/310 | null | gr-qc astro-ph hep-th quant-ph | null | This paper concerns the so-called cosmological constant problem. In order to
solve it, we propose a toy model providing an extension of the dimensionality
of spacetime, with an additional spatial dimension which is macroscopically
unobservable. The toy model introduces no corrections to most predictions of
the "standard" general relativity regarding, among others, the so-called "five
tests of general relativity". However, it seems that the toy model could
provide an explanation to the flatness of circular velocity curves of spiral
galaxies without introducing any dark matter. The proposed model has quite
important cosmological consequences. By introducing certain corrections to
Friedmann's currently accepted model(s), the toy model allows one to solve
problems related to the present density of matter in the Universe and, finally,
it does not contain the initial singularity.
| [
{
"created": "Mon, 19 Jul 2004 02:56:18 GMT",
"version": "v1"
},
{
"created": "Sat, 2 Oct 2004 19:55:31 GMT",
"version": "v2"
}
] | 2014-11-17 | [
[
"Tarkowski",
"Wojciech P.",
""
]
] | This paper concerns the so-called cosmological constant problem. In order to solve it, we propose a toy model providing an extension of the dimensionality of spacetime, with an additional spatial dimension which is macroscopically unobservable. The toy model introduces no corrections to most predictions of the "standard" general relativity regarding, among others, the so-called "five tests of general relativity". However, it seems that the toy model could provide an explanation to the flatness of circular velocity curves of spiral galaxies without introducing any dark matter. The proposed model has quite important cosmological consequences. By introducing certain corrections to Friedmann's currently accepted model(s), the toy model allows one to solve problems related to the present density of matter in the Universe and, finally, it does not contain the initial singularity. |
gr-qc/9602059 | null | M. Rainer | Classifying spaces for homogeneous manifolds and their related Lie
isometry deformations | Latex, 22 pages, 3 figures available as hardcopy | null | null | IPM-95-CCMP | gr-qc | null | Among plenty of applications, low-dimensional homogeneous spaces appear in
cosmological models as both, classical factor spaces of multidimensional
geometry and minisuperspaces in canonical quantization.
Here a new tool to restrict their continuous deformations is presented:
Classifying spaces for homogeneous manifolds and their related Lie isometry
deformations.
The adjoint representation of n-dimensional real Lie algebras induces a
natural topology on their classifying space, which encodes the natural
algebraic relationship between different Lie algebras therein. For n>1 this
topology is not Hausdorffian. Even more it satisfies only the separation axiom
T_0, but not T_1, i.e. there is a constant sequence which has a limit different
from the members of the sequence. Such a limit is called a transition.
Recently it was found that transitions are the natural generalization and
transitive completion of the well-known In\"on\"u-Wigner contractions. For n<5
the relational classifying spaces are constructed explicitly.
Calculating their characteristic scalar invariants via triad representations
of the characteristic isometry, local homogeneous Riemannian 3-spaces are
classified in their natural geometrical relations to each other. Their
classifying space is a composition of pieces with different isometry types.
Although it is Hausdorffian, different topological transitions to the same
limit may induce locally non-Euclidean regions (e.g. at Bianchi tppes VII_0).
| [
{
"created": "Wed, 28 Feb 1996 14:52:54 GMT",
"version": "v1"
}
] | 2016-08-31 | [
[
"Rainer",
"M.",
""
]
] | Among plenty of applications, low-dimensional homogeneous spaces appear in cosmological models as both, classical factor spaces of multidimensional geometry and minisuperspaces in canonical quantization. Here a new tool to restrict their continuous deformations is presented: Classifying spaces for homogeneous manifolds and their related Lie isometry deformations. The adjoint representation of n-dimensional real Lie algebras induces a natural topology on their classifying space, which encodes the natural algebraic relationship between different Lie algebras therein. For n>1 this topology is not Hausdorffian. Even more it satisfies only the separation axiom T_0, but not T_1, i.e. there is a constant sequence which has a limit different from the members of the sequence. Such a limit is called a transition. Recently it was found that transitions are the natural generalization and transitive completion of the well-known In\"on\"u-Wigner contractions. For n<5 the relational classifying spaces are constructed explicitly. Calculating their characteristic scalar invariants via triad representations of the characteristic isometry, local homogeneous Riemannian 3-spaces are classified in their natural geometrical relations to each other. Their classifying space is a composition of pieces with different isometry types. Although it is Hausdorffian, different topological transitions to the same limit may induce locally non-Euclidean regions (e.g. at Bianchi tppes VII_0). |
2004.04527 | Nelson Christensen | Jean-Yves Vinet, Nelson Christensen, Nicoleta Dinu-Jaeger, Michel
Lintz, Nary Man, Mikha\"el Pichot | Numerical solutions for phase noise due to pointing jitter with the LISA
telescope | null | J. Phys. Commun. 4 045005 (2020) | 10.1088/2399-6528/ab852e | null | gr-qc astro-ph.IM physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The aim of the Laser Interferometer Space Antenna (LISA) is to detect
gravitational waves through a phase modulation in long (2.5 Mkm) laser light
links between spacecraft. Among other noise sources to be addressed are the
phase fluctuations caused by a possible angular jitter of the emitted beam. The
present paper follows our preceding one (Vinet et al 2019 Class. Quant. Grav.
36, 205 003) based on an analytical study of the far field phase. We address
here a numerical treatment of the phase, to first order in the emitted
wavefront aberrations, but without any assumptions on the static bias term. We
verify that, in the phase change, the higher order terms in the static
mispointing are consistent with the results found in our preceding paper.
| [
{
"created": "Thu, 9 Apr 2020 13:15:26 GMT",
"version": "v1"
}
] | 2020-06-14 | [
[
"Vinet",
"Jean-Yves",
""
],
[
"Christensen",
"Nelson",
""
],
[
"Dinu-Jaeger",
"Nicoleta",
""
],
[
"Lintz",
"Michel",
""
],
[
"Man",
"Nary",
""
],
[
"Pichot",
"Mikhaël",
""
]
] | The aim of the Laser Interferometer Space Antenna (LISA) is to detect gravitational waves through a phase modulation in long (2.5 Mkm) laser light links between spacecraft. Among other noise sources to be addressed are the phase fluctuations caused by a possible angular jitter of the emitted beam. The present paper follows our preceding one (Vinet et al 2019 Class. Quant. Grav. 36, 205 003) based on an analytical study of the far field phase. We address here a numerical treatment of the phase, to first order in the emitted wavefront aberrations, but without any assumptions on the static bias term. We verify that, in the phase change, the higher order terms in the static mispointing are consistent with the results found in our preceding paper. |
2103.01140 | Axel Brandenburg | Axel Brandenburg, Grigol Gogoberidze, Tina Kahniashvili, Sayan Mandal,
Alberto Roper Pol, Nakul Shenoy | The scalar, vector, and tensor modes in gravitational wave turbulence
simulations | 25 pages, 8 figures | Class. Quantum Grav. 38, 145002 (2021) | 10.1088/1361-6382/ac011c | NORDITA-2021-019 | gr-qc astro-ph.CO physics.flu-dyn | http://creativecommons.org/licenses/by/4.0/ | We study the gravitational wave (GW) signal sourced by primordial turbulence
that is assumed to be present at cosmological phase transitions like the
electroweak and quantum chromodynamics phase transitions. We consider various
models of primordial turbulence, such as those with and without helicity,
purely hydrodynamical turbulence induced by fluid motions, and
magnetohydrodynamic turbulence whose energy can be dominated either by kinetic
or magnetic energy, depending on the nature of the turbulence. We also study
circularly polarized GWs generated by parity violating sources such as helical
turbulence. Our ultimate goal is to determine the efficiency of GW production
through different classes of turbulence. We find that the GW energy and strain
tend to be large for acoustic or irrotational turbulence, even though its
tensor mode amplitude is relatively small at most wave numbers. Only at very
small wave numbers is the spectral tensor mode significant, which might explain
the efficient GW production in that case.
| [
{
"created": "Mon, 1 Mar 2021 17:21:33 GMT",
"version": "v1"
},
{
"created": "Fri, 25 Jun 2021 03:34:32 GMT",
"version": "v2"
}
] | 2021-06-28 | [
[
"Brandenburg",
"Axel",
""
],
[
"Gogoberidze",
"Grigol",
""
],
[
"Kahniashvili",
"Tina",
""
],
[
"Mandal",
"Sayan",
""
],
[
"Pol",
"Alberto Roper",
""
],
[
"Shenoy",
"Nakul",
""
]
] | We study the gravitational wave (GW) signal sourced by primordial turbulence that is assumed to be present at cosmological phase transitions like the electroweak and quantum chromodynamics phase transitions. We consider various models of primordial turbulence, such as those with and without helicity, purely hydrodynamical turbulence induced by fluid motions, and magnetohydrodynamic turbulence whose energy can be dominated either by kinetic or magnetic energy, depending on the nature of the turbulence. We also study circularly polarized GWs generated by parity violating sources such as helical turbulence. Our ultimate goal is to determine the efficiency of GW production through different classes of turbulence. We find that the GW energy and strain tend to be large for acoustic or irrotational turbulence, even though its tensor mode amplitude is relatively small at most wave numbers. Only at very small wave numbers is the spectral tensor mode significant, which might explain the efficient GW production in that case. |
0808.0169 | Muhammad Akbar | M. Akbar | Viscous Cosmology and Thermodynamics of Apparent Horizon | 8 pages | Chin.Phys.Lett.25:4199-4202,2008 | 10.1088/0256-307X/25/12/004 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | It is shown that the differential form of Friedmann equations of FRW universe
can be recast as a similar form of the first law, $T_{h}dS_{h} = dE + WdV$, of
thermodynamics at the apparent horizon of FRW universe filled with the viscous
fluid. It is also shown that the generalized second law of thermodynamics holds
at the apparent horizon of FRW universe and preserves dominant energy
condition.
| [
{
"created": "Fri, 1 Aug 2008 18:35:17 GMT",
"version": "v1"
}
] | 2008-12-25 | [
[
"Akbar",
"M.",
""
]
] | It is shown that the differential form of Friedmann equations of FRW universe can be recast as a similar form of the first law, $T_{h}dS_{h} = dE + WdV$, of thermodynamics at the apparent horizon of FRW universe filled with the viscous fluid. It is also shown that the generalized second law of thermodynamics holds at the apparent horizon of FRW universe and preserves dominant energy condition. |
0809.1817 | Sergey Siparov | Sergey Siparov | Anisotropic geometrodynamics in cosmological problems | v3: numerical modelling added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The gravitation theory is modified on the base of geometric identity and
equivalence principle. This makes it possible to generalize the geodesics and
solve several problems of classical GRT such as flat rotation curves of the
spiral galaxies, Tully-Fisher law and some others and reveal the fundamental
(geometrical) origin of the cH acceleration value. The developed approach
contains all the results of the classical GRT and has promising cosmological
consequences.
| [
{
"created": "Wed, 10 Sep 2008 15:26:30 GMT",
"version": "v1"
},
{
"created": "Mon, 27 Oct 2008 09:23:18 GMT",
"version": "v2"
},
{
"created": "Sun, 2 Aug 2009 19:55:26 GMT",
"version": "v3"
}
] | 2009-08-02 | [
[
"Siparov",
"Sergey",
""
]
] | The gravitation theory is modified on the base of geometric identity and equivalence principle. This makes it possible to generalize the geodesics and solve several problems of classical GRT such as flat rotation curves of the spiral galaxies, Tully-Fisher law and some others and reveal the fundamental (geometrical) origin of the cH acceleration value. The developed approach contains all the results of the classical GRT and has promising cosmological consequences. |
2305.17413 | J. W. van Holten | J.W. van Holten | Dynamics of cosmological scalar fields | 14 pages, 6 figures | null | null | null | gr-qc astro-ph.CO | http://creativecommons.org/licenses/by-nc-nd/4.0/ | This paper reviews the dynamics of an isotropic and homogeneous cosmological
scalar field. A general approach to the solution of the Einstein-Klein-Gordon
equations is developed, which does not require slow-roll or other
approximations. General conclusions about the qualitative behaviour of the
solutions can be drawn, and examples of explicit solutions for some interesting
cases are given. It is also shown how to find scalar potentials giving rise to
a predetermined scalar field behaviour and associated evolution of the scale
factor.
| [
{
"created": "Sat, 27 May 2023 08:35:50 GMT",
"version": "v1"
}
] | 2023-05-30 | [
[
"van Holten",
"J. W.",
""
]
] | This paper reviews the dynamics of an isotropic and homogeneous cosmological scalar field. A general approach to the solution of the Einstein-Klein-Gordon equations is developed, which does not require slow-roll or other approximations. General conclusions about the qualitative behaviour of the solutions can be drawn, and examples of explicit solutions for some interesting cases are given. It is also shown how to find scalar potentials giving rise to a predetermined scalar field behaviour and associated evolution of the scale factor. |
gr-qc/0304038 | Janna Levin | John D. Barrow and Janna Levin (DAMTP) | The Copernican Principle in Compact Spacetimes | 5 pages | Mon.Not.Roy.Astron.Soc.346:615,2003 | 10.1046/j.1365-2966.2003.07117.x | null | gr-qc astro-ph | null | Copernicus realised we were not at the centre of the universe. A universe
made finite by topological identifications introduces a new Copernican
consideration: while we may not be at the geometric centre of the universe,
some galaxy could be. A finite universe also picks out a preferred frame: the
frame in which the universe is smallest. Although we are not likely to be at
the centre of the universe, we must live in the preferred frame (if we are at
rest with respect to the cosmological expansion). We show that the preferred
topological frame must also be the comoving frame in a homogeneous and
isotropic cosmological spacetime. Some implications of topologically
identifying time are also discussed.
| [
{
"created": "Wed, 9 Apr 2003 11:00:11 GMT",
"version": "v1"
}
] | 2011-05-23 | [
[
"Barrow",
"John D.",
"",
"DAMTP"
],
[
"Levin",
"Janna",
"",
"DAMTP"
]
] | Copernicus realised we were not at the centre of the universe. A universe made finite by topological identifications introduces a new Copernican consideration: while we may not be at the geometric centre of the universe, some galaxy could be. A finite universe also picks out a preferred frame: the frame in which the universe is smallest. Although we are not likely to be at the centre of the universe, we must live in the preferred frame (if we are at rest with respect to the cosmological expansion). We show that the preferred topological frame must also be the comoving frame in a homogeneous and isotropic cosmological spacetime. Some implications of topologically identifying time are also discussed. |
1208.1385 | S. Mignemi | S. Mignemi | Black brane solutions of Einstein-Maxwell-scalar theory with Liouville
potential | 17 pages, plain TeX, 1 figure; some errors have been corrected and
the discussion of the results modified accordingly | null | 10.1142/S0217751X13500802 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate the global properties of black brane solutions of a
three-parameter Einstein-Maxwell model nonminimally coupled to a scalar with
exponential potential. The black brane solutions of this model have recently
been investigated because of their relevance for holography and for the
AdS/condensed matter correspondence. We classify all the possible regular
solutions and show that they exist only for a limited range of values of the
parameters and that their asymptotic behavior either breaks hyperscaling
invariance or has the form of a domain wall. We also write down some exact
solutions in Schwarzschild coordinates.
| [
{
"created": "Tue, 7 Aug 2012 10:01:12 GMT",
"version": "v1"
},
{
"created": "Wed, 10 Apr 2013 08:31:58 GMT",
"version": "v2"
}
] | 2015-06-11 | [
[
"Mignemi",
"S.",
""
]
] | We investigate the global properties of black brane solutions of a three-parameter Einstein-Maxwell model nonminimally coupled to a scalar with exponential potential. The black brane solutions of this model have recently been investigated because of their relevance for holography and for the AdS/condensed matter correspondence. We classify all the possible regular solutions and show that they exist only for a limited range of values of the parameters and that their asymptotic behavior either breaks hyperscaling invariance or has the form of a domain wall. We also write down some exact solutions in Schwarzschild coordinates. |
gr-qc/9505004 | Andrew Chamblin | L. J. Alty and A. Chamblin | Obstructions to Pin Structures on Kleinian Manifolds | 20 pages, Latex, 2 xfigures available from Andrew Chamblin at
H.A.Chamblin@damtp.cam.ac.uk | J.Math.Phys. 37 (1996) 2001-2012 | 10.1063/1.531491 | DAMTP preprint # R94/58 | gr-qc | null | We develop various topological notions on four-manifolds of Kleinian
signature $(- - + +)$. In particular, we extend the concept of `Kleinian metric
homotopy' to non-orientable manifolds. We then derive the topological
obstructions to pin-Klein cobordism, for all of the pin groups. Finally, we
discuss various examples and applications which arise from this work.
| [
{
"created": "Wed, 3 May 1995 17:23:55 GMT",
"version": "v1"
}
] | 2009-10-28 | [
[
"Alty",
"L. J.",
""
],
[
"Chamblin",
"A.",
""
]
] | We develop various topological notions on four-manifolds of Kleinian signature $(- - + +)$. In particular, we extend the concept of `Kleinian metric homotopy' to non-orientable manifolds. We then derive the topological obstructions to pin-Klein cobordism, for all of the pin groups. Finally, we discuss various examples and applications which arise from this work. |
gr-qc/0405014 | Michal Demetrian | Michal Demetrian | False vacuum decay via Coleman - de Luccia instanton in the theory with
quasi-exponential potential | 2 pages, 1 figure | null | null | null | gr-qc | null | The necessary and sufficient condition for the false vacuum decay in a de
Sitter universe via Coleman - de Luccia instanton is applied on the scalar
field with quasi - exponential potential.
| [
{
"created": "Mon, 3 May 2004 16:10:45 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Demetrian",
"Michal",
""
]
] | The necessary and sufficient condition for the false vacuum decay in a de Sitter universe via Coleman - de Luccia instanton is applied on the scalar field with quasi - exponential potential. |
1306.2375 | Jong Hyuk Yoon | Jong Hyuk Yoon | Problem of time and Hamiltonian reduction in the (2+2) formalism | 4 pages, 1 figure in pdf | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We apply the Hamiltonian reduction procedure to general spacetimes of
4-dimensions in the (2+2) formalism and find privileged spacetime coordinates
in which the physical Hamiltonian is expressed in true degrees of freedom only,
namely, the conformal two-metric on the cross section of null hypersurfaces and
its conjugate momentum. The physical time is the area element of the cross
section of null hypersurface, and the physical radial coordinate is defined by
{\it equipotential} surfaces on a given spacelike hypersurface of constant
physical time. The physical Hamiltonian is {\it constraint-free} and manifestly
{\it positive-definite} in the privileged coordinates. We present the complete
set of the Hamilton's equations, and find that they coincide with the
Einstein's equations written in the privileged coordinates. This shows that our
Hamiltonian reduction is self-consistent and respects the general covariance.
This work is a generalization of ADM Hamiltonian reduction of midi-superspace
to 4-dimensional spacetimes with no isometries.
| [
{
"created": "Mon, 10 Jun 2013 22:40:03 GMT",
"version": "v1"
}
] | 2013-06-12 | [
[
"Yoon",
"Jong Hyuk",
""
]
] | We apply the Hamiltonian reduction procedure to general spacetimes of 4-dimensions in the (2+2) formalism and find privileged spacetime coordinates in which the physical Hamiltonian is expressed in true degrees of freedom only, namely, the conformal two-metric on the cross section of null hypersurfaces and its conjugate momentum. The physical time is the area element of the cross section of null hypersurface, and the physical radial coordinate is defined by {\it equipotential} surfaces on a given spacelike hypersurface of constant physical time. The physical Hamiltonian is {\it constraint-free} and manifestly {\it positive-definite} in the privileged coordinates. We present the complete set of the Hamilton's equations, and find that they coincide with the Einstein's equations written in the privileged coordinates. This shows that our Hamiltonian reduction is self-consistent and respects the general covariance. This work is a generalization of ADM Hamiltonian reduction of midi-superspace to 4-dimensional spacetimes with no isometries. |
1707.00723 | Jakub Bilski | Jakub Bilski and Antonino Marciano | 2+1 homogeneous Loop Quantum Gravity with a scalar field clock | 15 pages, typos corrected, cross-citation added | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We focus on three-dimensional QRLG with the purpose of shedding light on the
link between reduced LQG and LQC in four space-time dimensions. Considering
homogeneous three-dimensional LQG, the theory simplifies to QRLG. We then
implement Thiemann's Quantum Spin Dynamics for Euclidean three-dimensional
space-time in presence of a real scalar matter field. We deploy a polymer
quantization of the scalar field while using methods of quantum reduced loop
gravity. We compute the scalar Hamiltonian operator on the states of the
kinematical Hilbert space of the theory, and exhibit its matrix elements that
are derived using a new simplified method. The coupling to matter, which plays
the role of a carrier of dynamics, opens the pathway to the study of
phenomenological implications. We finally comment on the relations between
three-dimensional QRLG and LQC, as well as on the appearance of the
correspondence principle for the scalar field.
| [
{
"created": "Mon, 3 Jul 2017 18:34:37 GMT",
"version": "v1"
},
{
"created": "Wed, 5 Jul 2017 10:46:56 GMT",
"version": "v2"
}
] | 2017-07-06 | [
[
"Bilski",
"Jakub",
""
],
[
"Marciano",
"Antonino",
""
]
] | We focus on three-dimensional QRLG with the purpose of shedding light on the link between reduced LQG and LQC in four space-time dimensions. Considering homogeneous three-dimensional LQG, the theory simplifies to QRLG. We then implement Thiemann's Quantum Spin Dynamics for Euclidean three-dimensional space-time in presence of a real scalar matter field. We deploy a polymer quantization of the scalar field while using methods of quantum reduced loop gravity. We compute the scalar Hamiltonian operator on the states of the kinematical Hilbert space of the theory, and exhibit its matrix elements that are derived using a new simplified method. The coupling to matter, which plays the role of a carrier of dynamics, opens the pathway to the study of phenomenological implications. We finally comment on the relations between three-dimensional QRLG and LQC, as well as on the appearance of the correspondence principle for the scalar field. |
2008.12761 | James Lucietti | James Lucietti, Fred Tomlinson | Moduli space of stationary vacuum black holes from integrability | 58 pages. v2: typos fixed, minor clarifications, to appear in Adv.
Theor. Math. Phys | Adv. Theor. Math. Phys. Volume 26, Number 2, 371-454, 2022 | 10.4310/ATMP.2022.v26.n2.a4 | EMPG-20-16 | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the classification of asymptotically flat, stationary, vacuum
black hole spacetimes in four and five dimensions, that admit one and two
commuting axial Killing fields respectively. It is well known that the Einstein
equations reduce to a harmonic map on the two-dimensional orbit space, which
itself arises as the integrability condition for a linear system of spectral
equations. We integrate the Belinski-Zakharov spectral equations along the
boundary of the orbit space and use this to fully determine the metric and
associated Ernst and twist potentials on the axes and horizons. This is
sufficient to derive the moduli space of solutions that are free of conical
singularities on the axes, for any given rod structure. As an illustration of
this method we obtain constructive uniqueness proofs for the Kerr and
Myers-Perry black holes and the known doubly spinning black rings.
| [
{
"created": "Fri, 28 Aug 2020 17:36:48 GMT",
"version": "v1"
},
{
"created": "Tue, 8 Jun 2021 14:41:29 GMT",
"version": "v2"
}
] | 2023-01-05 | [
[
"Lucietti",
"James",
""
],
[
"Tomlinson",
"Fred",
""
]
] | We consider the classification of asymptotically flat, stationary, vacuum black hole spacetimes in four and five dimensions, that admit one and two commuting axial Killing fields respectively. It is well known that the Einstein equations reduce to a harmonic map on the two-dimensional orbit space, which itself arises as the integrability condition for a linear system of spectral equations. We integrate the Belinski-Zakharov spectral equations along the boundary of the orbit space and use this to fully determine the metric and associated Ernst and twist potentials on the axes and horizons. This is sufficient to derive the moduli space of solutions that are free of conical singularities on the axes, for any given rod structure. As an illustration of this method we obtain constructive uniqueness proofs for the Kerr and Myers-Perry black holes and the known doubly spinning black rings. |
1502.01386 | Fumika Suzuki | Fumika Suzuki and Friedemann Queisser | Environmental gravitational decoherence and a tensor noise model | 8 pages, 2 figures, based on a talk presented by FS at DICE 2014,
Castiglioncello, Italy, 15th-19th September 2014 | null | 10.1088/1742-6596/626/1/012039 | null | gr-qc quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss decrease of coherence in a massive system due to the emission of
gravitational waves. In particular we investigate environmental gravitational
decoherence in the context of an interference experiment. The time-evolution of
the reduced density matrix is solved analytically using the path-integral
formalism. Furthermore, we study the impact of a tensor noise onto the
coherence properties of massive systems. We discuss that a particular choice of
tensor noise shows similarities to a mechanism proposed by Diosi and Penrose.
| [
{
"created": "Wed, 4 Feb 2015 22:46:13 GMT",
"version": "v1"
}
] | 2015-07-09 | [
[
"Suzuki",
"Fumika",
""
],
[
"Queisser",
"Friedemann",
""
]
] | We discuss decrease of coherence in a massive system due to the emission of gravitational waves. In particular we investigate environmental gravitational decoherence in the context of an interference experiment. The time-evolution of the reduced density matrix is solved analytically using the path-integral formalism. Furthermore, we study the impact of a tensor noise onto the coherence properties of massive systems. We discuss that a particular choice of tensor noise shows similarities to a mechanism proposed by Diosi and Penrose. |
2204.10512 | Zhao Li | Zhao Li, Jin Qiao, Wen Zhao, Xinzhong Er | Gravitational Faraday rotation of gravitational waves by a Kerr black
hole | 13 pages, 1 figure, accepted by JCAP | null | 10.1088/1475-7516/2022/10/095 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Gravitational Faraday Rotation (GFR) is a frame-dragging effect induced by
rotating massive objects, which is one of the important, yet studied
characteristics of lensed gravitational waves (GWs). In this work, we calculate
the GFR angle $\chi_g$ of GWs in the weak deflection limit, assuming it is
lensed by a Kerr black hole (BH). We find that the GFR effect changes the
initial polarization state of the lensed GW. Compared with the Einstein
deflection angle, the dominant term of the rotation angle $\chi_g$ is a
second-order correction to the polarization angle, which depends on the
light-of-sight component of BH angular momentum. Such a rotation is tiny and
degenerates with the initial polarization angle. In some critical cases, the
GFR angle is close to the detection capability of the third-generation GW
detector network, although the degeneracy has to be broken.
| [
{
"created": "Fri, 22 Apr 2022 05:40:51 GMT",
"version": "v1"
},
{
"created": "Sun, 23 Oct 2022 13:08:18 GMT",
"version": "v2"
}
] | 2022-11-09 | [
[
"Li",
"Zhao",
""
],
[
"Qiao",
"Jin",
""
],
[
"Zhao",
"Wen",
""
],
[
"Er",
"Xinzhong",
""
]
] | Gravitational Faraday Rotation (GFR) is a frame-dragging effect induced by rotating massive objects, which is one of the important, yet studied characteristics of lensed gravitational waves (GWs). In this work, we calculate the GFR angle $\chi_g$ of GWs in the weak deflection limit, assuming it is lensed by a Kerr black hole (BH). We find that the GFR effect changes the initial polarization state of the lensed GW. Compared with the Einstein deflection angle, the dominant term of the rotation angle $\chi_g$ is a second-order correction to the polarization angle, which depends on the light-of-sight component of BH angular momentum. Such a rotation is tiny and degenerates with the initial polarization angle. In some critical cases, the GFR angle is close to the detection capability of the third-generation GW detector network, although the degeneracy has to be broken. |
gr-qc/0411022 | Marco Bruni | Marco Bruni, Andrea Nerozzi, Frances White | Newman-Penrose quantities as valuable tools in astrophysical relativity | 3 pages. Proceedings of 16th SIGRAV conference, Vietri, Italy,
September 2004 | null | 10.1063/1.1891553 | null | gr-qc astro-ph | null | In this talk I will briefly outline work in progress in two different
contexts in astrophysical relativity, i.e. the study of rotating star
spacetimes and the problem of reliably extracting gravitational wave templates
in numerical relativity. In both cases the use of Weyl scalars and curvature
invariants helps to clarify important issues.
| [
{
"created": "Wed, 3 Nov 2004 23:32:15 GMT",
"version": "v1"
}
] | 2009-11-10 | [
[
"Bruni",
"Marco",
""
],
[
"Nerozzi",
"Andrea",
""
],
[
"White",
"Frances",
""
]
] | In this talk I will briefly outline work in progress in two different contexts in astrophysical relativity, i.e. the study of rotating star spacetimes and the problem of reliably extracting gravitational wave templates in numerical relativity. In both cases the use of Weyl scalars and curvature invariants helps to clarify important issues. |
2001.04651 | Fabio D'Ambrosio | Fabio D'Ambrosio | Semi-Classical Holomorphic Transition Amplitudes in Covariant Loop
Quantum Gravity | Ph.D. thesis submitted for the degree of Doctor in Theoretical and
Mathematical Physics. Defended at the Center for Theoretical Physics of
Aix-Marseille University, the 23rd of September 2019. The manuscript is
written in English and begins with a short summary in French | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Covariant Loop Quantum Gravity (CLQG) is a tentative background-independent
and non-perturbative theory of quantum gravity which has emerged from a number
of different research directions. Recently, this theory has been applied to the
so-called Planck star model -- a particular model of stellar collapse in which
non-perturbative quantum gravity effects play a predominant role. However,
several obstacles have impeded progress in the investigation of this scenario.
These obstacles range from conceptual issues, such as the question how to
extract physical predictions from a background independent theory of quantum
gravity, to computational problems due to a lack of systematic methods to
evaluate CLQG transition amplitudes. This thesis addresses these problems
directly. It contains an analysis of the Planck star model within the framework
of CLQG, including a clarifying discussion on relevant conceptual issues.
Moreover, a new approximation method for CLQG transition amplitudes is
developed. This method allows to systematically study amplitudes in the
semi-classical regime of the theory and it sheds new light on the so-called
cosine problem.
| [
{
"created": "Tue, 14 Jan 2020 07:47:30 GMT",
"version": "v1"
}
] | 2020-01-15 | [
[
"D'Ambrosio",
"Fabio",
""
]
] | Covariant Loop Quantum Gravity (CLQG) is a tentative background-independent and non-perturbative theory of quantum gravity which has emerged from a number of different research directions. Recently, this theory has been applied to the so-called Planck star model -- a particular model of stellar collapse in which non-perturbative quantum gravity effects play a predominant role. However, several obstacles have impeded progress in the investigation of this scenario. These obstacles range from conceptual issues, such as the question how to extract physical predictions from a background independent theory of quantum gravity, to computational problems due to a lack of systematic methods to evaluate CLQG transition amplitudes. This thesis addresses these problems directly. It contains an analysis of the Planck star model within the framework of CLQG, including a clarifying discussion on relevant conceptual issues. Moreover, a new approximation method for CLQG transition amplitudes is developed. This method allows to systematically study amplitudes in the semi-classical regime of the theory and it sheds new light on the so-called cosine problem. |
2307.07285 | Tom\'a\v{s} M\'alek | Ivan Kol\'a\v{r}, Tom\'a\v{s} M\'alek | Infinite derivative gravity resolves nonscalar curvature singularities | 5 pages, 1 figure | Phys. Rev. D 108, L081502 (2023) | 10.1103/PhysRevD.108.L081502 | null | gr-qc hep-th | http://creativecommons.org/licenses/by/4.0/ | We explicitly demonstrate that the nonlocal ghost-free ultraviolet
modification of general relativity (GR) known as the infinite derivative
gravity (IDG) resolves nonscalar curvature singularities in exact solutions of
the full theory. We analyze exact pp-wave solutions of GR and IDG describing
gravitational waves generated by null radiation. Curvature of GR and IDG
solutions with the same energy-momentum tensor is compared in
parallel-propagated frames along timelike and null geodesics at finite values
of the affine parameter. While the GR pp-wave solution contains a physically
problematic nonscalar curvature singularity at the location of the source, the
curvature of its IDG counterpart is finite.
| [
{
"created": "Fri, 14 Jul 2023 11:35:25 GMT",
"version": "v1"
}
] | 2023-11-13 | [
[
"Kolář",
"Ivan",
""
],
[
"Málek",
"Tomáš",
""
]
] | We explicitly demonstrate that the nonlocal ghost-free ultraviolet modification of general relativity (GR) known as the infinite derivative gravity (IDG) resolves nonscalar curvature singularities in exact solutions of the full theory. We analyze exact pp-wave solutions of GR and IDG describing gravitational waves generated by null radiation. Curvature of GR and IDG solutions with the same energy-momentum tensor is compared in parallel-propagated frames along timelike and null geodesics at finite values of the affine parameter. While the GR pp-wave solution contains a physically problematic nonscalar curvature singularity at the location of the source, the curvature of its IDG counterpart is finite. |
2407.14693 | Francisco Cleiton Estev\~ao Lima | F. C. E. Lima, F. M. Belchior, C. A. S. Almeida and P. K. Sahoo | On the asymmetric non-canonical braneworld in five dimensions | 16 pages, 7 captioned figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | Revisiting Einstein's gravitational theory, we build a five-dimensional
braneworld. Within this framework, one announces the appearance of symmetric
and asymmetric domain walls. Furthermore, it examines the emergent
four-dimensional gravity from a theory with non-canonical dynamics. Exploring
the physical and mathematical aspects, e.g., brane's energy density and the
Kaluza-Klein (KK) spectrum, one verifies that brane splitting is absent in the
canonical and non-canonical theories. Additionally, we note the localization of
the four-dimensional fluctuation projection on the 3-branes, which ensures the
theory's stability. Thereby, one can conclude that the behavior of
gravitational perturbations of the domain wall maintains a profile similar to a
stable and non-localizable tower of massive modes. In contrast, within the
brane core, the matter sector generates new barriers and potential wells,
resulting in massive modes with approximately symmetric amplitudes. However,
the non-canonical dynamics generate massive modes with asymmetric amplitudes
far from the 3-brane.
| [
{
"created": "Fri, 19 Jul 2024 22:53:30 GMT",
"version": "v1"
},
{
"created": "Tue, 30 Jul 2024 18:14:31 GMT",
"version": "v2"
},
{
"created": "Wed, 7 Aug 2024 22:07:28 GMT",
"version": "v3"
}
] | 2024-08-09 | [
[
"Lima",
"F. C. E.",
""
],
[
"Belchior",
"F. M.",
""
],
[
"Almeida",
"C. A. S.",
""
],
[
"Sahoo",
"P. K.",
""
]
] | Revisiting Einstein's gravitational theory, we build a five-dimensional braneworld. Within this framework, one announces the appearance of symmetric and asymmetric domain walls. Furthermore, it examines the emergent four-dimensional gravity from a theory with non-canonical dynamics. Exploring the physical and mathematical aspects, e.g., brane's energy density and the Kaluza-Klein (KK) spectrum, one verifies that brane splitting is absent in the canonical and non-canonical theories. Additionally, we note the localization of the four-dimensional fluctuation projection on the 3-branes, which ensures the theory's stability. Thereby, one can conclude that the behavior of gravitational perturbations of the domain wall maintains a profile similar to a stable and non-localizable tower of massive modes. In contrast, within the brane core, the matter sector generates new barriers and potential wells, resulting in massive modes with approximately symmetric amplitudes. However, the non-canonical dynamics generate massive modes with asymmetric amplitudes far from the 3-brane. |
gr-qc/9502038 | David Wiltshire | D.L. Wiltshire | Dilaton black holes with a cosmological term | 20 pages, phyzzx, v2 contains expanded introduction, additional
references etc to coincide with published version | J.Austral.Math.Soc.B41:198-216,1999 | null | ADP-94-29/M26 | gr-qc | null | The properties of static spherically symmetric black holes, which carry
electric and magnetic charges, and which are coupled to the dilaton in the
presence of a cosmological term (Liouville-type potential, or cosmological
constant) are reviewed.
| [
{
"created": "Thu, 23 Feb 1995 08:43:19 GMT",
"version": "v1"
},
{
"created": "Wed, 13 Oct 1999 09:17:31 GMT",
"version": "v2"
}
] | 2008-11-26 | [
[
"Wiltshire",
"D. L.",
""
]
] | The properties of static spherically symmetric black holes, which carry electric and magnetic charges, and which are coupled to the dilaton in the presence of a cosmological term (Liouville-type potential, or cosmological constant) are reviewed. |
2307.04144 | Yu Zhang | Qian Li, Chen Ma, Yu Zhang, Zhi-Wen Lin, Peng-Fei Duan | Shadow, absorption and Hawking radiation of a Schwarzschild black hole
surrounded by a cloud of strings in Rastall gravity | 27 pages, 10 figures, 1 Table | Eur. Phys. J. C 82, 658 (2022) | 10.1140/epjc/s10052-022-10623-3 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper studies the black hole shadow, absorption cross section, and
Hawking radiation of a massless scalar field in the background of a static
spherically symmetric black hole spacetime that is surrounded by a cloud of
strings in Rastall gravity. Specifically, the effects of the parameters $a$ and
$\beta$ on the photon sphere and shadow radii are investigated. The results
show that as the negative parameter $\beta$ decreases, the photon sphere and
shadow radii change in an N-shape. In addition, the absorption cross section
obtained after solving the massless Klein-Gordon equation is calculated using
the sinc approximation and the partial waves method. We compare the absorption
cross section obtained by the sinc approximation and the partial waves method,
and find it to be exceptionally consistent in the mid-to-high frequency region.
Furthermore, the effects of parameters $a$ and $\beta$ on absorption are
examined in detail. Finally, we study in detail the effects of the parameters
$a$, $\beta$ and $l$ on the Hawking radiation power emission spectrum of the
considered black hole. It turns out that the string parameter $a$ always
suppresses the power emission spectrum, indicating that such black holes live
longer when the string parameter $a$ is increased while other parameters are
fixed.
| [
{
"created": "Sun, 9 Jul 2023 10:17:07 GMT",
"version": "v1"
}
] | 2023-07-11 | [
[
"Li",
"Qian",
""
],
[
"Ma",
"Chen",
""
],
[
"Zhang",
"Yu",
""
],
[
"Lin",
"Zhi-Wen",
""
],
[
"Duan",
"Peng-Fei",
""
]
] | This paper studies the black hole shadow, absorption cross section, and Hawking radiation of a massless scalar field in the background of a static spherically symmetric black hole spacetime that is surrounded by a cloud of strings in Rastall gravity. Specifically, the effects of the parameters $a$ and $\beta$ on the photon sphere and shadow radii are investigated. The results show that as the negative parameter $\beta$ decreases, the photon sphere and shadow radii change in an N-shape. In addition, the absorption cross section obtained after solving the massless Klein-Gordon equation is calculated using the sinc approximation and the partial waves method. We compare the absorption cross section obtained by the sinc approximation and the partial waves method, and find it to be exceptionally consistent in the mid-to-high frequency region. Furthermore, the effects of parameters $a$ and $\beta$ on absorption are examined in detail. Finally, we study in detail the effects of the parameters $a$, $\beta$ and $l$ on the Hawking radiation power emission spectrum of the considered black hole. It turns out that the string parameter $a$ always suppresses the power emission spectrum, indicating that such black holes live longer when the string parameter $a$ is increased while other parameters are fixed. |
1911.06483 | Liam O'Brien | Liam O'Brien and Lorenzo Sorbo | Instantons for particles joined by strings in three dimensional gravity | 13 pages, 4 figures | Class. Quantum Grav. 36 245008 (2019) | 10.1088/1361-6382/ab4a3e | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the instantons describing the production of particles at the ends of
codimension-one objects (strings and struts) in $(2+1)$-dimensional Minkowski
and de Sitter spaces. A Minkowskian background allows only for systems with
vanishing total mass, so that either negative mass particles or negative
tension struts are required. On a de Sitter background, on the other hand, we
find processes describing the production of string/particle systems with no
negative energies involved. We also compute the probabilities of creating and
of breaking an infinite cosmic string in de Sitter space. We perform our
analysis of the system in de Sitter space employing a generalization of the
toroidal coordinate system to the three-sphere.
| [
{
"created": "Fri, 15 Nov 2019 06:02:43 GMT",
"version": "v1"
}
] | 2019-11-18 | [
[
"O'Brien",
"Liam",
""
],
[
"Sorbo",
"Lorenzo",
""
]
] | We study the instantons describing the production of particles at the ends of codimension-one objects (strings and struts) in $(2+1)$-dimensional Minkowski and de Sitter spaces. A Minkowskian background allows only for systems with vanishing total mass, so that either negative mass particles or negative tension struts are required. On a de Sitter background, on the other hand, we find processes describing the production of string/particle systems with no negative energies involved. We also compute the probabilities of creating and of breaking an infinite cosmic string in de Sitter space. We perform our analysis of the system in de Sitter space employing a generalization of the toroidal coordinate system to the three-sphere. |
1505.00228 | Zoltan Keresztes | Zsolt Horv\'ath, Zolt\'an Keresztes, Alexander Yu. Kamenshchik,
L\'aszl\'o \'A. Gergely | Criticality and Big Brake singularities in the tachyonic evolutions of
closed Friedmann universes with cold dark matter | 7 pages, 5 figures, to be published in Phys. Rev. D | Phys. Rev. D 91, 103513 (2015) | 10.1103/PhysRevD.91.103513 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The evolution of a closed Friedmann universe filled by a tachyon scalar field
with a trigonometric potential and cold dark matter (CDM) is investigated. A
subset of the evolutions consistent to 1$\sigma $ confidence level with the
Union 2.1 supernova data set is identified. The evolutions of the tachyon field
are classified. Some of them evolve into a de Sitter attractor, while others
proceed through a pseudo-tachyonic regime into a sudden future singularity.
Critical evolutions leading to Big Brake singularities in the presence of CDM
are found and a new type of cosmological evolution characterized by singularity
avoidance in the pseudo-tachyon regime is presented.
| [
{
"created": "Fri, 1 May 2015 17:32:44 GMT",
"version": "v1"
}
] | 2015-05-21 | [
[
"Horváth",
"Zsolt",
""
],
[
"Keresztes",
"Zoltán",
""
],
[
"Kamenshchik",
"Alexander Yu.",
""
],
[
"Gergely",
"László Á.",
""
]
] | The evolution of a closed Friedmann universe filled by a tachyon scalar field with a trigonometric potential and cold dark matter (CDM) is investigated. A subset of the evolutions consistent to 1$\sigma $ confidence level with the Union 2.1 supernova data set is identified. The evolutions of the tachyon field are classified. Some of them evolve into a de Sitter attractor, while others proceed through a pseudo-tachyonic regime into a sudden future singularity. Critical evolutions leading to Big Brake singularities in the presence of CDM are found and a new type of cosmological evolution characterized by singularity avoidance in the pseudo-tachyon regime is presented. |
1301.5481 | Hermann Nicolai | Hermann Nicolai | Quantum Gravity: the view from particle physics | Invited Lecture at the conference "Relativity and Gravitation: 100
Years after Einstein in Prague", June 25 - 29, 2012, Prague, Czech Republic | null | 10.1007/978-3-319-06349-2_18 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This lecture reviews aspects of and prospects for progress towards a theory
of quantum gravity from a particle physics perspective, also paying attention
to recent findings of the LHC experiments at CERN.
| [
{
"created": "Wed, 23 Jan 2013 12:11:33 GMT",
"version": "v1"
}
] | 2015-06-12 | [
[
"Nicolai",
"Hermann",
""
]
] | This lecture reviews aspects of and prospects for progress towards a theory of quantum gravity from a particle physics perspective, also paying attention to recent findings of the LHC experiments at CERN. |
2302.10695 | I. V. Kanatchikov | I.V. Kanatchikov | Towards Precanonical Quantum Teleparallel Gravity | 17 pages | null | null | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantization of the teleparallel equivalent of general relativity (TEGR) is
discussed from the perspective of the space-time symmetric De Donder-Weyl (DW)
Hamiltonian formulation with constraints and its quantization called
precanonical quantization. The representations of operators and the covariant
Schr\"odinger equation for TEGR are obtained from the quantization of
generalized Dirac brackets calculated according to the analysis of constraints
within the polysymplectic formulation of the DW Hamiltonian theory. We argue
that the appropriate treatment of the operator ordering and the generalized
Hermicity of operators results in an additional $c$-number term in the DW
Hamiltonian operator which is identified with the cosmological constant and
estimated to be consistent with its observed value.
| [
{
"created": "Tue, 21 Feb 2023 14:26:03 GMT",
"version": "v1"
}
] | 2023-02-22 | [
[
"Kanatchikov",
"I. V.",
""
]
] | Quantization of the teleparallel equivalent of general relativity (TEGR) is discussed from the perspective of the space-time symmetric De Donder-Weyl (DW) Hamiltonian formulation with constraints and its quantization called precanonical quantization. The representations of operators and the covariant Schr\"odinger equation for TEGR are obtained from the quantization of generalized Dirac brackets calculated according to the analysis of constraints within the polysymplectic formulation of the DW Hamiltonian theory. We argue that the appropriate treatment of the operator ordering and the generalized Hermicity of operators results in an additional $c$-number term in the DW Hamiltonian operator which is identified with the cosmological constant and estimated to be consistent with its observed value. |
2306.11101 | Mariaveronica De Angelis | Giovanni Montani, Mariaveronica De Angelis, Flavio Bombacigno, Nakia
Carlevaro | Metric $f(R)$ gravity with dynamical dark energy as a scenario for the
Hubble tension | 6 pages, 4 figures | Mon.Not.Roy.Astron.Soc. Letters 527 (2024) 1, L156-L161 | 10.1093/mnrasl/slad159 | null | gr-qc astro-ph.CO | http://creativecommons.org/publicdomain/zero/1.0/ | We introduce a theoretical framework to interpret the Hubble tension, based
on the combination of a metric $f(R)$ gravity with a dynamical dark energy
contribution. The modified gravity provides the non-minimally coupled scalar
field responsible for the proper scaling of the Hubble constant, in order to
accommodate for the local SNIa pantheon+ data and Planck measurements. The
dynamical dark energy source, which exhibits a phantom divide line separating
the low red-shift quintessence regime ($-1<w<-1/3$) from the phantom
contribution ($w<-1$) in the early Universe, guarantees the absence of
tachyonic instabilities at low red-shift. The resulting $H_0(z)$ profile
rapidly approaches the Planck value, with a plateau behaviour for $z\gtrsim 5$.
In this scenario, the Hubble tension emerges as a low red-shift effect, which
can be in principle tested by comparing SNIa predictions with far sources, like
QUASARS and Gamma Ray Bursts.
| [
{
"created": "Mon, 19 Jun 2023 18:08:06 GMT",
"version": "v1"
},
{
"created": "Fri, 3 Nov 2023 09:52:49 GMT",
"version": "v2"
}
] | 2023-11-07 | [
[
"Montani",
"Giovanni",
""
],
[
"De Angelis",
"Mariaveronica",
""
],
[
"Bombacigno",
"Flavio",
""
],
[
"Carlevaro",
"Nakia",
""
]
] | We introduce a theoretical framework to interpret the Hubble tension, based on the combination of a metric $f(R)$ gravity with a dynamical dark energy contribution. The modified gravity provides the non-minimally coupled scalar field responsible for the proper scaling of the Hubble constant, in order to accommodate for the local SNIa pantheon+ data and Planck measurements. The dynamical dark energy source, which exhibits a phantom divide line separating the low red-shift quintessence regime ($-1<w<-1/3$) from the phantom contribution ($w<-1$) in the early Universe, guarantees the absence of tachyonic instabilities at low red-shift. The resulting $H_0(z)$ profile rapidly approaches the Planck value, with a plateau behaviour for $z\gtrsim 5$. In this scenario, the Hubble tension emerges as a low red-shift effect, which can be in principle tested by comparing SNIa predictions with far sources, like QUASARS and Gamma Ray Bursts. |
gr-qc/0207114 | Gavriel Segre | Gavriel Segre | Einstein's lifts and topologies: topological investigations on the
Principle of Equivalence | null | null | null | null | gr-qc | null | The gedanken-experiment of Einstein's lift is analyzed in order of
determining whether the free-falling observer inside the lift can detect the
eventual topological non-triviality of space-time
| [
{
"created": "Sun, 28 Jul 2002 16:56:36 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Segre",
"Gavriel",
""
]
] | The gedanken-experiment of Einstein's lift is analyzed in order of determining whether the free-falling observer inside the lift can detect the eventual topological non-triviality of space-time |
1405.0519 | Francisco Lobo | Tiberiu Harko, Francisco S. N. Lobo, G. Otalora, Emmanuel N. Saridakis | $f(T,\mathcal{T})$ gravity and cosmology | 31 pages, 15 figures; matches published version | JCAP 12 (2014) 021 | 10.1088/1475-7516/2014/12/021 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present an extension of $f(T)$ gravity, allowing for a general coupling of
the torsion scalar $T$ with the trace of the matter energy-momentum tensor
$\mathcal{T}$. The resulting $f(T,\mathcal{T})$ theory is a new modified
gravity, since it is different from all the existing torsion or curvature based
constructions. Applied to a cosmological framework, it leads to interesting
phenomenology. In particular, one can obtain a unified description of the
initial inflationary phase, the subsequent non-accelerating, matter-dominated
expansion, and then the transition to a late-time accelerating phase.
Additionally, the effective dark energy sector can be quintessence or
phantom-like, or exhibit the phantom-divide crossing during the evolution.
Moreover, in the far future the universe results either to a de Sitter
exponential expansion, or to eternal power-law accelerated expansions. Finally,
a detailed study of the scalar perturbations at the linear level reveals that
$f(T,\mathcal{T})$ cosmology can be free of ghosts and instabilities for a wide
class of ansatzes and model parameters.
| [
{
"created": "Fri, 2 May 2014 21:37:45 GMT",
"version": "v1"
},
{
"created": "Wed, 7 May 2014 11:37:12 GMT",
"version": "v2"
},
{
"created": "Thu, 11 Dec 2014 18:50:50 GMT",
"version": "v3"
}
] | 2014-12-12 | [
[
"Harko",
"Tiberiu",
""
],
[
"Lobo",
"Francisco S. N.",
""
],
[
"Otalora",
"G.",
""
],
[
"Saridakis",
"Emmanuel N.",
""
]
] | We present an extension of $f(T)$ gravity, allowing for a general coupling of the torsion scalar $T$ with the trace of the matter energy-momentum tensor $\mathcal{T}$. The resulting $f(T,\mathcal{T})$ theory is a new modified gravity, since it is different from all the existing torsion or curvature based constructions. Applied to a cosmological framework, it leads to interesting phenomenology. In particular, one can obtain a unified description of the initial inflationary phase, the subsequent non-accelerating, matter-dominated expansion, and then the transition to a late-time accelerating phase. Additionally, the effective dark energy sector can be quintessence or phantom-like, or exhibit the phantom-divide crossing during the evolution. Moreover, in the far future the universe results either to a de Sitter exponential expansion, or to eternal power-law accelerated expansions. Finally, a detailed study of the scalar perturbations at the linear level reveals that $f(T,\mathcal{T})$ cosmology can be free of ghosts and instabilities for a wide class of ansatzes and model parameters. |
1201.2948 | Jose' P. S. Lemos | Alexander B. Balakin, Vladimir V. Bochkarev, Jos\'e P. S. Lemos | Light propagation with non-minimal couplings in a two-component cosmic
dark fluid with an Archimedean-type force and unlighted cosmological epochs | 23 pages, 8 figures | Phys.Rev.D85:064015,2012 | 10.1103/PhysRevD.85.064015 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | During the evolution of the universe there are at least two epochs during
which electromagnetic waves cannot scan the universe's internal structure
neither bring information to outside observers. The first epoch is when photons
are in local thermodynamic equilibrium with other particles, and the second is
when photon scattering by charged particles is strong. One can call these two
periods of cosmological time as standard unlighted epochs. After the last
scattering surface, photons become relic photons and turn into a source of
information about the universe. Unlighted cosmic epochs can also appear when
one considers non-minimal theories, i.e., theories in which the electromagnetic
field is coupled in an intricate way with the cosmological gravitational field.
By considering a cosmological model where the dark sector, i.e., the dark
energy and dark matter, self-interacts via an Archimedean-type force, and
taking into account a non-minimal coupling theory for the electromagnetic
field, we discuss the appearance of unlighted epochs. In the framework of our
non-minimal theory, a three-parameter non-minimal Einstein-Maxwell model, the
curvature coupling can be formulated in terms of an effective refraction index
n(t). Then, taking advantage of a well-known classical analogy, namely, in a
medium with n^2<0 electromagnetic waves do not propagate and their group
velocity, i.e., energy transfer velocity, has zero value at the boundary of the
corresponding zone, one can search for the unlighted epochs arising in the
interacting dark fluid cosmological model. We study here, both analytically and
numerically, cosmological models admitting unlighted epochs.
| [
{
"created": "Fri, 13 Jan 2012 21:02:20 GMT",
"version": "v1"
}
] | 2012-11-08 | [
[
"Balakin",
"Alexander B.",
""
],
[
"Bochkarev",
"Vladimir V.",
""
],
[
"Lemos",
"José P. S.",
""
]
] | During the evolution of the universe there are at least two epochs during which electromagnetic waves cannot scan the universe's internal structure neither bring information to outside observers. The first epoch is when photons are in local thermodynamic equilibrium with other particles, and the second is when photon scattering by charged particles is strong. One can call these two periods of cosmological time as standard unlighted epochs. After the last scattering surface, photons become relic photons and turn into a source of information about the universe. Unlighted cosmic epochs can also appear when one considers non-minimal theories, i.e., theories in which the electromagnetic field is coupled in an intricate way with the cosmological gravitational field. By considering a cosmological model where the dark sector, i.e., the dark energy and dark matter, self-interacts via an Archimedean-type force, and taking into account a non-minimal coupling theory for the electromagnetic field, we discuss the appearance of unlighted epochs. In the framework of our non-minimal theory, a three-parameter non-minimal Einstein-Maxwell model, the curvature coupling can be formulated in terms of an effective refraction index n(t). Then, taking advantage of a well-known classical analogy, namely, in a medium with n^2<0 electromagnetic waves do not propagate and their group velocity, i.e., energy transfer velocity, has zero value at the boundary of the corresponding zone, one can search for the unlighted epochs arising in the interacting dark fluid cosmological model. We study here, both analytically and numerically, cosmological models admitting unlighted epochs. |
2209.00868 | Zheng-Wen Long | Meng-Yao Zhang, Hao Chen, Hassan Hassanabadi, Zheng-Wen Long, and Hui
Yang | Joule-Thomson expansion of charged dilatonic black holes | null | Chinese Physics C (2022) | 10.1088/1674-1137/aca958 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Based on the Einstein-Maxwell theory, the Joule-Thomson (J-T) expansion of
charged dilatonic black holes (the solutions are neither flat nor AdS) in
$(n+1)$-dimensional spacetime is studied herein. To this end, we analyze the
effects of the dimension $n$ and dilaton field $\alpha$ on J-T expansion. An
explicit expression for the J-T coefficient is derived, and consequently, a
negative heat capacity is found to lead to a cooling process. In contrast to
its effect on the dimension, the inversion curve decreases with charge $Q$ at
low pressures, whereas the opposite effect is observed at high pressures. We
can observe that with an increase in the dimension $n$ or parameter $\alpha$,
both the pressure cut-off point and the minimum inversion temperature $T_{min}$
change. Moreover, we analyze the ratio $T_{min}/T_{c}$ numerically and discover
that the ratio is independent of charge; however, it depends on the dilaton
field and dimension: for $n=3$ and $\alpha=0$, the ratio is 1/2. The dilaton
field is found to enhance the ratio. In addition, we identify the
cooling-heating regions by investigating the inversion and isenthalpic curves,
and the behavior of the minimum inversion mass $M_{min}$ indicates that this
cooling-heating transition may not occur under certain special conditions.
| [
{
"created": "Fri, 2 Sep 2022 07:59:15 GMT",
"version": "v1"
},
{
"created": "Wed, 21 Sep 2022 02:58:49 GMT",
"version": "v2"
},
{
"created": "Tue, 6 Dec 2022 08:11:50 GMT",
"version": "v3"
},
{
"created": "Thu, 16 Feb 2023 07:21:14 GMT",
"version": "v4"
}
] | 2023-02-17 | [
[
"Zhang",
"Meng-Yao",
""
],
[
"Chen",
"Hao",
""
],
[
"Hassanabadi",
"Hassan",
""
],
[
"Long",
"Zheng-Wen",
""
],
[
"Yang",
"Hui",
""
]
] | Based on the Einstein-Maxwell theory, the Joule-Thomson (J-T) expansion of charged dilatonic black holes (the solutions are neither flat nor AdS) in $(n+1)$-dimensional spacetime is studied herein. To this end, we analyze the effects of the dimension $n$ and dilaton field $\alpha$ on J-T expansion. An explicit expression for the J-T coefficient is derived, and consequently, a negative heat capacity is found to lead to a cooling process. In contrast to its effect on the dimension, the inversion curve decreases with charge $Q$ at low pressures, whereas the opposite effect is observed at high pressures. We can observe that with an increase in the dimension $n$ or parameter $\alpha$, both the pressure cut-off point and the minimum inversion temperature $T_{min}$ change. Moreover, we analyze the ratio $T_{min}/T_{c}$ numerically and discover that the ratio is independent of charge; however, it depends on the dilaton field and dimension: for $n=3$ and $\alpha=0$, the ratio is 1/2. The dilaton field is found to enhance the ratio. In addition, we identify the cooling-heating regions by investigating the inversion and isenthalpic curves, and the behavior of the minimum inversion mass $M_{min}$ indicates that this cooling-heating transition may not occur under certain special conditions. |
2206.03814 | Lorenzo Sebastiani | Lorenzo Sebastiani and Sergio Zerbini | Some remarks on non-singular spherically symmetric space-times | 25 pages, final version accepted in Astronomy | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | A short review on spherically symmetric static regular black holes and
spherically symmetric non singular cosmological space-time is presented.
Several models of regular black holes, including new ones, are considered.
First, a large class of regular black holes having an inner de Sitter core with
the related issue of Cauchy horizon is investigated. Then, black bounce
space-times, where the Cauchy horizon and therefore the related instabilities
are absent, are discussed as valid alternatives of regular black holes with
inner de Sitter core. Friedman-Lemaitre-Robertson-Walker space-times admitting
regular bounce solutions are also discussed. In the general analysis concerning
the presence or absence of singularities in the equations of motion, the role
of a theorem due to Osgood is stressed.
| [
{
"created": "Wed, 8 Jun 2022 11:25:17 GMT",
"version": "v1"
},
{
"created": "Sat, 15 Oct 2022 07:11:48 GMT",
"version": "v2"
},
{
"created": "Wed, 23 Nov 2022 14:33:42 GMT",
"version": "v3"
}
] | 2022-11-24 | [
[
"Sebastiani",
"Lorenzo",
""
],
[
"Zerbini",
"Sergio",
""
]
] | A short review on spherically symmetric static regular black holes and spherically symmetric non singular cosmological space-time is presented. Several models of regular black holes, including new ones, are considered. First, a large class of regular black holes having an inner de Sitter core with the related issue of Cauchy horizon is investigated. Then, black bounce space-times, where the Cauchy horizon and therefore the related instabilities are absent, are discussed as valid alternatives of regular black holes with inner de Sitter core. Friedman-Lemaitre-Robertson-Walker space-times admitting regular bounce solutions are also discussed. In the general analysis concerning the presence or absence of singularities in the equations of motion, the role of a theorem due to Osgood is stressed. |
2105.09174 | Cosimo Bambi | Bakhtiyor Narzilloev, Daniele Malafarina, Ahmadjon Abdujabbarov,
Bobomurat Ahmedo, Cosimo Bambi | Particle motion around a static axially symmetric wormhole | 12 pages, 9 figures; v2: refereed version | Phys. Rev. D 104, 064016 (2021) | 10.1103/PhysRevD.104.064016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the properties of a static axially symmetric wormhole described
by an exact solution of Einstein's field equations and investigate how we can
distinguish such a hypothetical object from a black hole. To this aim, we
explore the motion of test particles and photons in the wormhole's space-time
and compare it with the particle dynamics in the well known space-times of
Schwarzschild and Kerr black holes. We show that precise simultaneous
measurement of test particle motion and photon motion may provide the means to
distinguish the wormhole geometry from that of a black hole.
| [
{
"created": "Wed, 19 May 2021 14:45:24 GMT",
"version": "v1"
},
{
"created": "Tue, 7 Sep 2021 20:39:43 GMT",
"version": "v2"
}
] | 2021-09-09 | [
[
"Narzilloev",
"Bakhtiyor",
""
],
[
"Malafarina",
"Daniele",
""
],
[
"Abdujabbarov",
"Ahmadjon",
""
],
[
"Ahmedo",
"Bobomurat",
""
],
[
"Bambi",
"Cosimo",
""
]
] | We consider the properties of a static axially symmetric wormhole described by an exact solution of Einstein's field equations and investigate how we can distinguish such a hypothetical object from a black hole. To this aim, we explore the motion of test particles and photons in the wormhole's space-time and compare it with the particle dynamics in the well known space-times of Schwarzschild and Kerr black holes. We show that precise simultaneous measurement of test particle motion and photon motion may provide the means to distinguish the wormhole geometry from that of a black hole. |
2010.05755 | Francisco Lobo | Khadije Jafarzade, Mahdi Kord Zangeneh, Francisco S. N. Lobo | Shadow, deflection angle and quasinormal modes of Born-Infeld charged
black holes | 10 pages, 4 figures- V2: Analysis improved with the consistent
Aoki-Gorji-Mukohyama theory of 4D EGB gravity with BI nonlinear
electrodynamics. Discussion and references added; abstract improved. Accepted
for publication in JCAP. arXiv admin note: text overlap with arXiv:2009.12988 | JCAP 04 (2021) 008 | 10.1088/1475-7516/2021/04/008 | null | gr-qc astro-ph.HE hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we consider black holes in the consistent Aoki-Gorji-Mukohyama
theory of the four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity in the
presence of Born-Infeld (BI) nonlinear electrodynamics. We study several
optical features of these black holes such as the shadow radius, energy
emission rate and deflection angle, and analyse the effect of the coupling
constants, the electric charge and cosmological constant on the considered
optical quantities. Furthermore, we also employ the connection between the
shadow radius and quasinormal modes (QNMs) and investigate small scalar
perturbations around the black hole solution. We show that the variation of the
parameters of the theory provide specific signatures on the optical features of
the BI charged black hole solution, thus leading to the possibility of directly
testing this consistent Aoki-Gorji-Mukohyama 4D EGB black hole model by using
astrophysical observations.
| [
{
"created": "Thu, 8 Oct 2020 09:48:51 GMT",
"version": "v1"
},
{
"created": "Wed, 24 Feb 2021 16:14:23 GMT",
"version": "v2"
}
] | 2021-04-07 | [
[
"Jafarzade",
"Khadije",
""
],
[
"Zangeneh",
"Mahdi Kord",
""
],
[
"Lobo",
"Francisco S. N.",
""
]
] | In this paper, we consider black holes in the consistent Aoki-Gorji-Mukohyama theory of the four-dimensional Einstein-Gauss-Bonnet (4D EGB) gravity in the presence of Born-Infeld (BI) nonlinear electrodynamics. We study several optical features of these black holes such as the shadow radius, energy emission rate and deflection angle, and analyse the effect of the coupling constants, the electric charge and cosmological constant on the considered optical quantities. Furthermore, we also employ the connection between the shadow radius and quasinormal modes (QNMs) and investigate small scalar perturbations around the black hole solution. We show that the variation of the parameters of the theory provide specific signatures on the optical features of the BI charged black hole solution, thus leading to the possibility of directly testing this consistent Aoki-Gorji-Mukohyama 4D EGB black hole model by using astrophysical observations. |
1907.10301 | Alexander Ganz | Alexander Ganz, Nicola Bartolo, Sabino Matarrese | Towards a viable effective field theory of mimetic gravity | null | null | 10.1088/1475-7516/2019/12/037 | null | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We discuss mimetic gravity theories with direct couplings between the
curvature and higher derivatives of the scalar field, up to the quintic order,
which were proposed to solve the instability problem for linear perturbations
around the FLRW background for this kind of models. Restricting to homogeneous
scalar field configurations in the action, we derive degeneracy conditions to
obtain an effective field theory with three degrees of freedom. However,
performing the Hamiltonian analysis for a generic scalar field we show that
there are in general four or more degrees of freedom. The discrepancy is
resolved because, for a homogeneous scalar field profile,
$\partial_i\varphi\approx 0$, the Dirac matrix becomes singular, resulting in
further constraints, which reduces the number of degrees of freedom to three.
Similarly, in linear perturbation theory the additional scalar degree of
freedom can only be seen by considering a non-homogeneous background profile of
the scalar field. Therefore, restricting to homogeneous scalar fields these
kinds of models provide viable explicitly Lorentz violating effective field
theories of mimetic gravity.
| [
{
"created": "Wed, 24 Jul 2019 08:48:34 GMT",
"version": "v1"
}
] | 2019-12-18 | [
[
"Ganz",
"Alexander",
""
],
[
"Bartolo",
"Nicola",
""
],
[
"Matarrese",
"Sabino",
""
]
] | We discuss mimetic gravity theories with direct couplings between the curvature and higher derivatives of the scalar field, up to the quintic order, which were proposed to solve the instability problem for linear perturbations around the FLRW background for this kind of models. Restricting to homogeneous scalar field configurations in the action, we derive degeneracy conditions to obtain an effective field theory with three degrees of freedom. However, performing the Hamiltonian analysis for a generic scalar field we show that there are in general four or more degrees of freedom. The discrepancy is resolved because, for a homogeneous scalar field profile, $\partial_i\varphi\approx 0$, the Dirac matrix becomes singular, resulting in further constraints, which reduces the number of degrees of freedom to three. Similarly, in linear perturbation theory the additional scalar degree of freedom can only be seen by considering a non-homogeneous background profile of the scalar field. Therefore, restricting to homogeneous scalar fields these kinds of models provide viable explicitly Lorentz violating effective field theories of mimetic gravity. |
2203.14039 | Chen Songbai | Jiayi Liu, Songbai Chen, Jiliang Jing | Tidal effects of dark matter halo around a galactic black hole | 14 pages, 6 figures, Accepted by Chin. Phys. C | Chin. Phys. C 46, 105104 (2022) | 10.1088/1674-1137/ac7856 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We have investigated the tidal forces and geodesic deviation motion in the
spacetime of a black hole in the galaxy with dark matter halo. Our results show
that the tidal force and geodesic deviation motion depend on the dark matter
halo mass and the typical lengthscale of galaxy. The effect of the typical
lengthscale of galaxy on tidal force is opposite to that of dark matter mass.
For the radial tidal force, with the increasing mass of dark matter, it
increases in the region far from the black hole, but decreases in the region
near black hole. For the angular tidal force, its absolute value of angular
tidal force monotonously increases with the dark matter halo mass. Especially,
the angular tidal force also depends on the particle's energy and the effects
of dark matter become more distinct for the test particle with high energy,
which is different from those in the usual static black hole spacetimes. We
also present the change of geodesic deviation vector with the dark matter halo
mass and the typical lengthscale of galaxy under two kinds of initial
conditions.
| [
{
"created": "Sat, 26 Mar 2022 10:07:41 GMT",
"version": "v1"
},
{
"created": "Sat, 4 Jun 2022 09:56:06 GMT",
"version": "v2"
}
] | 2022-09-07 | [
[
"Liu",
"Jiayi",
""
],
[
"Chen",
"Songbai",
""
],
[
"Jing",
"Jiliang",
""
]
] | We have investigated the tidal forces and geodesic deviation motion in the spacetime of a black hole in the galaxy with dark matter halo. Our results show that the tidal force and geodesic deviation motion depend on the dark matter halo mass and the typical lengthscale of galaxy. The effect of the typical lengthscale of galaxy on tidal force is opposite to that of dark matter mass. For the radial tidal force, with the increasing mass of dark matter, it increases in the region far from the black hole, but decreases in the region near black hole. For the angular tidal force, its absolute value of angular tidal force monotonously increases with the dark matter halo mass. Especially, the angular tidal force also depends on the particle's energy and the effects of dark matter become more distinct for the test particle with high energy, which is different from those in the usual static black hole spacetimes. We also present the change of geodesic deviation vector with the dark matter halo mass and the typical lengthscale of galaxy under two kinds of initial conditions. |
0709.0442 | Miquel Nofrarias | M. Nofrarias, A. F. Garcia Marin, A. Lobo, G. Heinzel, J.
Ramos-Castro, J. Sanjuan and K. Danzmann | Thermal diagnostic of the Optical Window on board LISA Pathfinder | 20 pages, 14 figures; accepted for publication in Class. Quantum Grav | Class.Quant.Grav.24:5103-5122,2007 | 10.1088/0264-9381/24/20/012 | null | gr-qc | null | Vacuum conditions inside the LTP Gravitational Reference Sensor must comply
with rather demanding requirements. The Optical Window (OW) is an interface
which seals the vacuum enclosure and, at the same time, lets the laser beam go
through for interferometric Metrology with the test masses. The OW is a
plane-parallel plate clamped in a Titanium flange, and is considerably
sensitive to thermal and stress fluctuations. It is critical for the required
precision measurements, hence its temperature will be carefully monitored in
flight. This paper reports on the results of a series of OW characterisation
laboratory runs, intended to study its response to selected thermal signals, as
well as their fit to numerical models, and the meaning of the latter. We find
that a single pole ARMA transfer function provides a consistent approximation
to the OW response to thermal excitations, and derive a relationship with the
physical processes taking place in the OW. We also show how system noise
reduction can be accomplished by means of that transfer function.
| [
{
"created": "Tue, 4 Sep 2007 14:30:39 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Nofrarias",
"M.",
""
],
[
"Marin",
"A. F. Garcia",
""
],
[
"Lobo",
"A.",
""
],
[
"Heinzel",
"G.",
""
],
[
"Ramos-Castro",
"J.",
""
],
[
"Sanjuan",
"J.",
""
],
[
"Danzmann",
"K.",
""
]
] | Vacuum conditions inside the LTP Gravitational Reference Sensor must comply with rather demanding requirements. The Optical Window (OW) is an interface which seals the vacuum enclosure and, at the same time, lets the laser beam go through for interferometric Metrology with the test masses. The OW is a plane-parallel plate clamped in a Titanium flange, and is considerably sensitive to thermal and stress fluctuations. It is critical for the required precision measurements, hence its temperature will be carefully monitored in flight. This paper reports on the results of a series of OW characterisation laboratory runs, intended to study its response to selected thermal signals, as well as their fit to numerical models, and the meaning of the latter. We find that a single pole ARMA transfer function provides a consistent approximation to the OW response to thermal excitations, and derive a relationship with the physical processes taking place in the OW. We also show how system noise reduction can be accomplished by means of that transfer function. |
gr-qc/0011043 | Kenichi Sasaki | M. Hotta, K. Sasaki, T. Sasaki | Diffeomorphism on Horizon as an Asymptotic Isometry of Schwarzschild
Black Hole | 18 pages, no figures, corrected some typos | Class.Quant.Grav. 18 (2001) 1823-1834 | 10.1088/0264-9381/18/10/301 | TU-606 | gr-qc hep-th | null | It is argued that the diffeomorphism on the horizontal sphere can be regarded
as a nontrivial asymptotic isometry of the Schwarzschild black hole. We propose
a new boundary condition of asymptotic metrics near the horizon and show that
the condition admits the local time-shift and diffeomorphism on the horizon as
the asymptotic symmetry.
| [
{
"created": "Mon, 13 Nov 2000 06:25:59 GMT",
"version": "v1"
},
{
"created": "Tue, 14 Nov 2000 01:57:01 GMT",
"version": "v2"
},
{
"created": "Thu, 15 Mar 2001 03:42:56 GMT",
"version": "v3"
}
] | 2009-10-31 | [
[
"Hotta",
"M.",
""
],
[
"Sasaki",
"K.",
""
],
[
"Sasaki",
"T.",
""
]
] | It is argued that the diffeomorphism on the horizontal sphere can be regarded as a nontrivial asymptotic isometry of the Schwarzschild black hole. We propose a new boundary condition of asymptotic metrics near the horizon and show that the condition admits the local time-shift and diffeomorphism on the horizon as the asymptotic symmetry. |
2203.03763 | Phillipo Lappicy | Kevin E. M. Church, Olivier H\'enot, Phillipo Lappicy, Jean-Philippe
Lessard and Hauke Sprink | Periodic orbits in Ho\v{r}ava-Lifshitz cosmologies | 21 pages, 7 figures. arXiv admin note: text overlap with
arXiv:2012.07614 | null | 10.1007/s10714-022-03054-8 | null | gr-qc math-ph math.CA math.DS math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider spatially homogeneous Ho\v{r}ava-Lifshitz (HL) models that
perturb General Relativity (GR) by a parameter $v\in (0,1)$ such that GR occurs
at $v=1/2$. We describe the dynamics for the extremal case $v=0$, which possess
the usual Bianchi hierarchy: type $\mathrm{I}$ (Kasner circle of equilibria),
type $\mathrm{II}$ (heteroclinics that induce the Kasner map) and type
$\mathrm{VI_0},\mathrm{VII_0}$ (further heteroclinics). For type
$\mathrm{VIII}$ and $\mathrm{IX}$, we use a computer-assisted approach to prove
the existence of periodic orbits which are far from the Mixmaster attractor and
thereby we obtain a new behaviour which is not described by the BKL picture of
bouncing Kasner-like states.
| [
{
"created": "Mon, 7 Mar 2022 22:57:49 GMT",
"version": "v1"
},
{
"created": "Wed, 7 Dec 2022 21:19:10 GMT",
"version": "v2"
}
] | 2022-12-28 | [
[
"Church",
"Kevin E. M.",
""
],
[
"Hénot",
"Olivier",
""
],
[
"Lappicy",
"Phillipo",
""
],
[
"Lessard",
"Jean-Philippe",
""
],
[
"Sprink",
"Hauke",
""
]
] | We consider spatially homogeneous Ho\v{r}ava-Lifshitz (HL) models that perturb General Relativity (GR) by a parameter $v\in (0,1)$ such that GR occurs at $v=1/2$. We describe the dynamics for the extremal case $v=0$, which possess the usual Bianchi hierarchy: type $\mathrm{I}$ (Kasner circle of equilibria), type $\mathrm{II}$ (heteroclinics that induce the Kasner map) and type $\mathrm{VI_0},\mathrm{VII_0}$ (further heteroclinics). For type $\mathrm{VIII}$ and $\mathrm{IX}$, we use a computer-assisted approach to prove the existence of periodic orbits which are far from the Mixmaster attractor and thereby we obtain a new behaviour which is not described by the BKL picture of bouncing Kasner-like states. |
gr-qc/9412052 | Hartmut Frommert | H. Dehnen and E. Hitzer | SU(2) $\times$ U(1) Gauge Gravity | 24 pages, latex, no figures | Int.J.Theor.Phys.34:1981-2001,1995 | 10.1007/BF00674079 | null | gr-qc hep-th | null | We propose a Lorentz-covariant Yang-Mills ``spin-gauge'' theory, where the
function valued Pauli matrices play the role of a non-scalar Higgs-field. As
symmetry group we choose $SU(2) \times U(1)$ of the 2-spinors describing
particle/antiparticle states. After symmetry breaking a non-scalar
Lorentz-covariant Higgs-field gravity appears, which can be interpreted within
a classical limit as Einstein's metrical theory of gravity, where we restrict
ourselves in a first step to its linearized version.
| [
{
"created": "Tue, 20 Dec 1994 10:42:19 GMT",
"version": "v1"
}
] | 2008-11-26 | [
[
"Dehnen",
"H.",
""
],
[
"Hitzer",
"E.",
""
]
] | We propose a Lorentz-covariant Yang-Mills ``spin-gauge'' theory, where the function valued Pauli matrices play the role of a non-scalar Higgs-field. As symmetry group we choose $SU(2) \times U(1)$ of the 2-spinors describing particle/antiparticle states. After symmetry breaking a non-scalar Lorentz-covariant Higgs-field gravity appears, which can be interpreted within a classical limit as Einstein's metrical theory of gravity, where we restrict ourselves in a first step to its linearized version. |
1106.2287 | Ritabrata Biswas | Ritabrata Biswas, Nairwita Mazumder and Subenoy Chakraborty | Evolution of the horizons for dark energy universe | 11 pages | null | 10.1007/s10773-012-1239-y | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Recent observational evidences of accelerating phase of the universe strongly
demand that the dominating matter in the universe is in the form of dark
energy. In this work, we study the evolution of the apparent and event horizons
for various dark energy models and examine their behavior across phantom
barrier line.
| [
{
"created": "Sun, 12 Jun 2011 08:11:21 GMT",
"version": "v1"
}
] | 2015-05-28 | [
[
"Biswas",
"Ritabrata",
""
],
[
"Mazumder",
"Nairwita",
""
],
[
"Chakraborty",
"Subenoy",
""
]
] | Recent observational evidences of accelerating phase of the universe strongly demand that the dominating matter in the universe is in the form of dark energy. In this work, we study the evolution of the apparent and event horizons for various dark energy models and examine their behavior across phantom barrier line. |
1311.6872 | Dong-han Yeom | Dong-il Hwang, Dong-han Yeom | Toward inflation models compatible with the no-boundary proposal | 34 pages, 14 figures | JCAP 1406(2014)007 | 10.1088/1475-7516/2014/06/007 | YITP-13-122 | gr-qc astro-ph.CO hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we investigate various inflation models in the context of the
no-boundary proposal. We propose that a good inflation model should satisfy
three conditions: observational constraints, plausible initial conditions, and
naturalness of the model. For various inflation models, we assign the
probability to each initial condition using the no-boundary proposal and define
a quantitative standard, typicality, to check whether the model satisfies the
observational constraints with probable initial conditions. There are three
possible ways to satisfy the typicality criterion: there was pre-inflation near
the high energy scale, the potential is finely tuned or the inflationary field
space is unbounded, or there are sufficient number of fields that contribute to
inflation. The no-boundary proposal rejects some of naive inflation models,
explains some of traditional doubts on inflation, and possibly, can have
observational consequences.
| [
{
"created": "Wed, 27 Nov 2013 05:38:02 GMT",
"version": "v1"
},
{
"created": "Fri, 6 Jun 2014 01:53:17 GMT",
"version": "v2"
}
] | 2014-06-09 | [
[
"Hwang",
"Dong-il",
""
],
[
"Yeom",
"Dong-han",
""
]
] | In this paper, we investigate various inflation models in the context of the no-boundary proposal. We propose that a good inflation model should satisfy three conditions: observational constraints, plausible initial conditions, and naturalness of the model. For various inflation models, we assign the probability to each initial condition using the no-boundary proposal and define a quantitative standard, typicality, to check whether the model satisfies the observational constraints with probable initial conditions. There are three possible ways to satisfy the typicality criterion: there was pre-inflation near the high energy scale, the potential is finely tuned or the inflationary field space is unbounded, or there are sufficient number of fields that contribute to inflation. The no-boundary proposal rejects some of naive inflation models, explains some of traditional doubts on inflation, and possibly, can have observational consequences. |
2108.06294 | Alexander Vikman | C\'edric Deffayet, Shinji Mukohyama, Alexander Vikman | Ghosts without runaway | 4 pages + refs, 4 figures | null | null | YITP-21-82, IPMU21-0052 | gr-qc astro-ph.CO hep-th | http://creativecommons.org/licenses/by/4.0/ | We present a simple class of mechanical models where a canonical degree of
freedom interacts with another one with a negative kinetic term, i.e. with a
ghost. We prove analytically that the classical motion of the system is
completely stable for all initial conditions, notwithstanding that the
conserved Hamiltonian is unbounded from below and above. This is fully
supported by numerical computations. Systems with negative kinetic terms often
appear in modern cosmology, quantum gravity and high energy physics and are
usually deemed as unstable. Our result demonstrates that for mechanical systems
this common lore can be too naive and that living with ghosts can be stable.
| [
{
"created": "Fri, 13 Aug 2021 15:57:49 GMT",
"version": "v1"
}
] | 2021-08-16 | [
[
"Deffayet",
"Cédric",
""
],
[
"Mukohyama",
"Shinji",
""
],
[
"Vikman",
"Alexander",
""
]
] | We present a simple class of mechanical models where a canonical degree of freedom interacts with another one with a negative kinetic term, i.e. with a ghost. We prove analytically that the classical motion of the system is completely stable for all initial conditions, notwithstanding that the conserved Hamiltonian is unbounded from below and above. This is fully supported by numerical computations. Systems with negative kinetic terms often appear in modern cosmology, quantum gravity and high energy physics and are usually deemed as unstable. Our result demonstrates that for mechanical systems this common lore can be too naive and that living with ghosts can be stable. |
2111.00283 | Torben Frost | Torben C. Frost | Gravitational Lensing by Charged Accelerating Black Holes | Submitted Conference Proceedings for 16th Marcel Grossmann Meeting,
fixed typos/formulations | null | 10.1142/9789811269776_0323 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Current astrophysical observations show that on large scale the Universe is
electrically neutral. However, locally this may be quite different. Black holes
enveloped by a plasma in the presence of a strong magnetic field may have
acquired a significant electric charge. We can also expect that some of these
charged black holes are moving. Consequently to describe them we need spacetime
metrics describing moving black holes. In general relativity such a solution is
given by the charged C-de Sitter-metric. In this article we will assume that it
can be used to describe moving charged black holes. We will investigate how to
observe the electric charge using gravitational lensing. First we will use
elliptic integrals and functions to solve the geodesic equations. Then we will
derive lens equation, travel time and redshift. We will discuss the impact of
the electric charge on these observables and potential limitations for its
observation.
| [
{
"created": "Sat, 30 Oct 2021 16:28:12 GMT",
"version": "v1"
},
{
"created": "Fri, 5 Nov 2021 17:04:59 GMT",
"version": "v2"
}
] | 2023-04-04 | [
[
"Frost",
"Torben C.",
""
]
] | Current astrophysical observations show that on large scale the Universe is electrically neutral. However, locally this may be quite different. Black holes enveloped by a plasma in the presence of a strong magnetic field may have acquired a significant electric charge. We can also expect that some of these charged black holes are moving. Consequently to describe them we need spacetime metrics describing moving black holes. In general relativity such a solution is given by the charged C-de Sitter-metric. In this article we will assume that it can be used to describe moving charged black holes. We will investigate how to observe the electric charge using gravitational lensing. First we will use elliptic integrals and functions to solve the geodesic equations. Then we will derive lens equation, travel time and redshift. We will discuss the impact of the electric charge on these observables and potential limitations for its observation. |
2404.04192 | Edward Wilson-Ewing | Lorenzo Cipriani, Francesco Fazzini, Edward Wilson-Ewing | Gravitational collapse in effective loop quantum gravity: beyond
marginally bound configurations | 36 pages, 9 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study gravitational collapse in effective loop quantum gravity, focusing
on non-marginally bound configurations in Lema\^itre-Tolman-Bondi spacetimes.
In the homogeneous limit we recover the effective dynamics of loop quantum
cosmology for Friedman cosmologies with spatial curvature. We study a
particular family of configurations with a homogeneous interior and a sharp
boundary where the dust energy density rapidly and continuously decreases to
zero. For these configurations, the gravitational collapse continues to the
Planck regime when a bounce occurs, at which point the dust ball starts to
expand, and a shock wave forms in the gravitational field within the order of a
Planck time after the bounce. The shock slowly moves outwards, eventually
reaching the horizon which then disappears, at which time there is no longer a
black hole. If the initial configuration is bound, the shock asymptotes to a
maximal radius, whereas for unbound initial configurations the shock escapes to
infinity. In all cases, the black hole lifetime is proportional to the square
of the black hole mass, and additionally depends on how strongly bound the dust
profile is; this last quantity also affects the vacuum region outside the dust
profile which is not solely determined by the black hole mass and charge as in
spherically symmetric general relativity. We also use numerics to study a wide
range of other types of initial configurations, both bound and unbound, with
qualitatively similar results.
| [
{
"created": "Fri, 5 Apr 2024 16:04:23 GMT",
"version": "v1"
}
] | 2024-04-08 | [
[
"Cipriani",
"Lorenzo",
""
],
[
"Fazzini",
"Francesco",
""
],
[
"Wilson-Ewing",
"Edward",
""
]
] | We study gravitational collapse in effective loop quantum gravity, focusing on non-marginally bound configurations in Lema\^itre-Tolman-Bondi spacetimes. In the homogeneous limit we recover the effective dynamics of loop quantum cosmology for Friedman cosmologies with spatial curvature. We study a particular family of configurations with a homogeneous interior and a sharp boundary where the dust energy density rapidly and continuously decreases to zero. For these configurations, the gravitational collapse continues to the Planck regime when a bounce occurs, at which point the dust ball starts to expand, and a shock wave forms in the gravitational field within the order of a Planck time after the bounce. The shock slowly moves outwards, eventually reaching the horizon which then disappears, at which time there is no longer a black hole. If the initial configuration is bound, the shock asymptotes to a maximal radius, whereas for unbound initial configurations the shock escapes to infinity. In all cases, the black hole lifetime is proportional to the square of the black hole mass, and additionally depends on how strongly bound the dust profile is; this last quantity also affects the vacuum region outside the dust profile which is not solely determined by the black hole mass and charge as in spherically symmetric general relativity. We also use numerics to study a wide range of other types of initial configurations, both bound and unbound, with qualitatively similar results. |
gr-qc/0409050 | Richard O'Shaughenssy | R. O'Shaughnessy, S. Strigin, S. Vyatchanin | The implications of Mexican-hat mirrors: calculations of thermoelastic
noise and interferometer sensitivity to perturbation for the
Mexican-hat-mirror proposal for advanced LIGO | Submitted to PRD. This paper is a close companion to a related paper,
"Reducing thermoelastic noise in gravitational interferometers by flattening
the light beams", by D'Ambrosio et al | null | null | null | gr-qc | null | Thermoelastic noise will be the most significant noise source in
advanced-LIGO interferometers with sapphire test masses. The standard plan for
advanced-LIGO has optimized the optics, within the framework of conventional
mirrors, to reduce thermoelastic noise. Recently, we and our collaborators have
proposed going beyond the bounds of traditional optics to increase the
effective beam spot size and thus lower thermoelastic noise. One particular
proposal for mirror shapes (``Mexican-hat mirrors'') yields the class of
``mesa'' beams.
In this paper, we outline a general procedure for analyzing light propagating
in individual arm cavities, and the associated thermoelastic noise, in the
presence of arbitrary optics. We apply these procedures to study the
Mexican-hat proposal. Results obtained by the techniques of this paper were
presented elsewhere, to demonstrate that the Mexican-hat proposal for
advanced-LIGO both significantly lowers thermoelastic noise and does not
significantly complicate the function of the interferometer.
| [
{
"created": "Mon, 13 Sep 2004 01:43:07 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"O'Shaughnessy",
"R.",
""
],
[
"Strigin",
"S.",
""
],
[
"Vyatchanin",
"S.",
""
]
] | Thermoelastic noise will be the most significant noise source in advanced-LIGO interferometers with sapphire test masses. The standard plan for advanced-LIGO has optimized the optics, within the framework of conventional mirrors, to reduce thermoelastic noise. Recently, we and our collaborators have proposed going beyond the bounds of traditional optics to increase the effective beam spot size and thus lower thermoelastic noise. One particular proposal for mirror shapes (``Mexican-hat mirrors'') yields the class of ``mesa'' beams. In this paper, we outline a general procedure for analyzing light propagating in individual arm cavities, and the associated thermoelastic noise, in the presence of arbitrary optics. We apply these procedures to study the Mexican-hat proposal. Results obtained by the techniques of this paper were presented elsewhere, to demonstrate that the Mexican-hat proposal for advanced-LIGO both significantly lowers thermoelastic noise and does not significantly complicate the function of the interferometer. |
1906.05957 | Valerio Faraoni | Valerio Faraoni, Jeremy C\^ot\'e, Andrea Giusti | Do Solar System experiments constrain scalar-tensor gravity? | Explanation added, bibliography expanded. Matches the version
accepted in Eur. Phys. J. C | null | 10.1140/epjc/s10052-020-7721-4 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is now established that, contrary to common belief, (electro-)vacuum
Brans-Dicke gravity does not reduce to general relativity for large values of
the Brans-Dicke coupling $\omega$. Since the essence of experimental tests of
scalar-tensor gravity consists of providing stringent lower bounds on $\omega$,
the PPN formalism on which these tests are based could be in jeopardy. We show
that, in the linearized approximation used by the PPN formalism, the anomaly in
the limit to general relativity disappears. However, it survives to second (and
higher) order and in strong gravity. This fact is relevant for experiments
aiming to test second order light deflection and Shapiro time delay.
| [
{
"created": "Thu, 13 Jun 2019 22:50:34 GMT",
"version": "v1"
},
{
"created": "Fri, 7 Feb 2020 19:23:47 GMT",
"version": "v2"
}
] | 2020-03-18 | [
[
"Faraoni",
"Valerio",
""
],
[
"Côté",
"Jeremy",
""
],
[
"Giusti",
"Andrea",
""
]
] | It is now established that, contrary to common belief, (electro-)vacuum Brans-Dicke gravity does not reduce to general relativity for large values of the Brans-Dicke coupling $\omega$. Since the essence of experimental tests of scalar-tensor gravity consists of providing stringent lower bounds on $\omega$, the PPN formalism on which these tests are based could be in jeopardy. We show that, in the linearized approximation used by the PPN formalism, the anomaly in the limit to general relativity disappears. However, it survives to second (and higher) order and in strong gravity. This fact is relevant for experiments aiming to test second order light deflection and Shapiro time delay. |
gr-qc/9404024 | Genadi A. Sardanashvily | G.Sardanashvily (Department of Theoretical Physics, Moscow State
University, Moscow, Russia) | Gravitation Singularities of the Caustic Type | LaTeX Preprint MSU-TP-94-31 | null | null | null | gr-qc | null | In view of the well-known correspondence between gravitational fields and
space-time distributions on a world manifold X, the criterion of gravitation
singularities as singularities of these distributions is suggested. In the germ
terms, singularities of a (3+1) distribution look locally like singularities of
a foliation whose leaves are level surfaces of a real function f on X. If f is
a single-valued function, changes of leave topology at critical points of f
take place. In case of a multi-valued function f, one can lift the foliation to
the total space of the cotangent bundle over X, then extend it over branch
points of f and project this extension onto X. Singular points of this
projection constitute a Lagrange map caustic by Arnol'd.
| [
{
"created": "Wed, 13 Apr 1994 10:02:20 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Sardanashvily",
"G.",
"",
"Department of Theoretical Physics, Moscow State\n University, Moscow, Russia"
]
] | In view of the well-known correspondence between gravitational fields and space-time distributions on a world manifold X, the criterion of gravitation singularities as singularities of these distributions is suggested. In the germ terms, singularities of a (3+1) distribution look locally like singularities of a foliation whose leaves are level surfaces of a real function f on X. If f is a single-valued function, changes of leave topology at critical points of f take place. In case of a multi-valued function f, one can lift the foliation to the total space of the cotangent bundle over X, then extend it over branch points of f and project this extension onto X. Singular points of this projection constitute a Lagrange map caustic by Arnol'd. |
0812.1645 | Gerhard Rein | Hakan Andreasson, Markus Kunze, Gerhard Rein | Gravitational collapse and the formation of black holes for the
spherically symmetric Einstein-Vlasov system | 35 pages | Q.Appl.Math.68:17-42,2010 | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We review results on the spherically symmetric, asymptotically flat
Einstein-Vlasov system. We focus on a recent result where we found explicit
conditions on the initial data which guarantee the formation of a black hole in
the evolution. Among these data there are data such that the corresponding
solutions exist globally in Schwarzschild coordinates. We put these results
into a more general context, and we include arguments which show that the
spacetimes we obtain satisfy the weak cosmic censorship conjecture and contain
a black hole in the sense of suitable mathematical definitions of these
concepts which are available in the literature.
| [
{
"created": "Tue, 9 Dec 2008 10:09:54 GMT",
"version": "v1"
}
] | 2011-02-24 | [
[
"Andreasson",
"Hakan",
""
],
[
"Kunze",
"Markus",
""
],
[
"Rein",
"Gerhard",
""
]
] | We review results on the spherically symmetric, asymptotically flat Einstein-Vlasov system. We focus on a recent result where we found explicit conditions on the initial data which guarantee the formation of a black hole in the evolution. Among these data there are data such that the corresponding solutions exist globally in Schwarzschild coordinates. We put these results into a more general context, and we include arguments which show that the spacetimes we obtain satisfy the weak cosmic censorship conjecture and contain a black hole in the sense of suitable mathematical definitions of these concepts which are available in the literature. |
1403.5910 | Daniele Faccio | N. Westerberg, S. Cacciatori, F. Belgiorno, F. Dalla Piazza and D.
Faccio | Experimental quantum cosmology in time-dependent optical media | Version accepted fro publication in New Journal of Physics | null | 10.1088/1367-2630/16/7/075003 | null | gr-qc physics.optics quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is possible to construct artificial spacetime geometries for light by
using intense laser pulses that modify the spatiotemporal properties of an
optical medium. Here we theoretically investigate experimental possibilities
for studying spacetime metrics of the form
$\textrm{d}s^2=c^2\textrm{d}t^2-\eta(t)^2\textrm{d}x^2$. By tailoring the laser
pulse shape and medium properties, it is possible to create a refractive index
variation $n=n(t)$ that can be identified with $\eta(t)$. Starting from a
perturbative solution to a generalised Hopfield model for the medium described
by an $n=n(t)$ we provide estimates for the number of photons generated by the
time-dependent spacetime. The simplest example is that of a uniformly varying
$\eta(t)$ that therefore describes the Robertson-Walker metric, i.e. a
cosmological expansion. The number of photon pairs generated in experimentally
feasible conditions appears to be extremely small. However, large photon
production can be obtained by periodically modulating the medium and thus
resorting to a resonant enhancement similar to that observed in the dynamical
Casimir effect. Curiously, the spacetime metric in this case closely resembles
that of a gravitational wave. Motivated by this analogy we show that a periodic
gravitational wave can indeed act as an amplifier for photons. The emission for
an actual gravitational wave will be very weak but should be readily observable
in the laboratory analogue.
| [
{
"created": "Mon, 24 Mar 2014 10:58:22 GMT",
"version": "v1"
},
{
"created": "Wed, 14 May 2014 14:47:56 GMT",
"version": "v2"
}
] | 2015-06-19 | [
[
"Westerberg",
"N.",
""
],
[
"Cacciatori",
"S.",
""
],
[
"Belgiorno",
"F.",
""
],
[
"Piazza",
"F. Dalla",
""
],
[
"Faccio",
"D.",
""
]
] | It is possible to construct artificial spacetime geometries for light by using intense laser pulses that modify the spatiotemporal properties of an optical medium. Here we theoretically investigate experimental possibilities for studying spacetime metrics of the form $\textrm{d}s^2=c^2\textrm{d}t^2-\eta(t)^2\textrm{d}x^2$. By tailoring the laser pulse shape and medium properties, it is possible to create a refractive index variation $n=n(t)$ that can be identified with $\eta(t)$. Starting from a perturbative solution to a generalised Hopfield model for the medium described by an $n=n(t)$ we provide estimates for the number of photons generated by the time-dependent spacetime. The simplest example is that of a uniformly varying $\eta(t)$ that therefore describes the Robertson-Walker metric, i.e. a cosmological expansion. The number of photon pairs generated in experimentally feasible conditions appears to be extremely small. However, large photon production can be obtained by periodically modulating the medium and thus resorting to a resonant enhancement similar to that observed in the dynamical Casimir effect. Curiously, the spacetime metric in this case closely resembles that of a gravitational wave. Motivated by this analogy we show that a periodic gravitational wave can indeed act as an amplifier for photons. The emission for an actual gravitational wave will be very weak but should be readily observable in the laboratory analogue. |
gr-qc/0401091 | Lorenzo Iorio | Lorenzo Iorio | On the Possibility of Measuring the Lense--Thirring Effect with a
Lageos-Lageos II-Optis Mission | LaTex2e, 3 pages, 1 Table, no figures. Paper presented at X Marcel
Grossmann Meeting, Rio de Janeiro, 20-26 July 2003 | null | 10.1142/9789812704030_0272 | null | gr-qc astro-ph physics.space-ph | null | The possibility of performing post-Newtonian gravitoelectromagnetic
measurements with a joint LAGEOS-LAGEOS II-OPTIS space-based mission is
investigated
| [
{
"created": "Wed, 21 Jan 2004 20:54:07 GMT",
"version": "v1"
}
] | 2016-11-09 | [
[
"Iorio",
"Lorenzo",
""
]
] | The possibility of performing post-Newtonian gravitoelectromagnetic measurements with a joint LAGEOS-LAGEOS II-OPTIS space-based mission is investigated |
2008.04816 | Dishant Pandya M | B. Thakore, R. Goti, S. Shah, H. Pandya and D. M. Pandya | Finch-Skea Solutions of Anisotropic Stellar Models in $f(R)$ Gravity | 24 Pages, 19 Figures and 5 Tables | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Present paper deals with the composition and modelling of compact dense
astrophysical bodies under the framework of $f(R)$ gravity. The model is
employed on various observed strange stars viz., SMC X-1, SAX J1808.4-3658,
Swift J1818.0-1607, PSR J1614-2230 and PSR J0348+0432. Upon setting the
appropriate value of dimensionless coupling parameter $\lambda $, the physical
parameters such as the density, the radial and tangential pressures were
obtained. Mass-Radius relation without presuming any equation of state is
capable enough to accommodate all strange stars nearly having solar mass up to
2.5. The physical viability of the model is examined for all the aforementioned
stars and it is found that all the regularity and stability conditions are
satisfied.
| [
{
"created": "Sun, 9 Aug 2020 17:41:25 GMT",
"version": "v1"
}
] | 2020-08-12 | [
[
"Thakore",
"B.",
""
],
[
"Goti",
"R.",
""
],
[
"Shah",
"S.",
""
],
[
"Pandya",
"H.",
""
],
[
"Pandya",
"D. M.",
""
]
] | Present paper deals with the composition and modelling of compact dense astrophysical bodies under the framework of $f(R)$ gravity. The model is employed on various observed strange stars viz., SMC X-1, SAX J1808.4-3658, Swift J1818.0-1607, PSR J1614-2230 and PSR J0348+0432. Upon setting the appropriate value of dimensionless coupling parameter $\lambda $, the physical parameters such as the density, the radial and tangential pressures were obtained. Mass-Radius relation without presuming any equation of state is capable enough to accommodate all strange stars nearly having solar mass up to 2.5. The physical viability of the model is examined for all the aforementioned stars and it is found that all the regularity and stability conditions are satisfied. |
2309.11468 | Pradip Kumar Chattopadhyay Dr. | B. Das, K. B. Goswami and P. K. Chattopadhyay | A comparative study on maximum mass and radius of compact star from
Heintzmann geometry and TOV approach | 27 pages, 21 figures | null | null | null | gr-qc | http://creativecommons.org/licenses/by-nc-nd/4.0/ | In this article a class of anisotropic compact star is analysed in Heintzmann
geometry. We have introduced the pressure anisotropy parameter ($\alpha$) and
solved Einstein field equations to obtain stellar model. We have considered
$g_{tt}$ component as proposed by Heintzmann and by solving Einstein field
equation, the $g_{rr}$ component is evaluated in presence of pressure
anisotropy. It is noted that for isotropic star ($\alpha=0$), the maximum mass
lies within the range $1.87-3.04~ M_{\odot}$ for radii ranges between $8-13$
Km. For anisotropic compact stars maximum mass increases with $\alpha$ and lies
within the range $1.99-3.23~ M_{\odot}$ for anisotropy parameter $\alpha=0.5$.
The physical viability of the model is examined by applying our model to study
the properties of few known compact objects. It is noted that all the stability
conditions are fulfilled in the proposed model. It is interesting to note that
maximum mass calculated from our model and from solving TOV equation are
approximately same and also the predicted radius of few newly observed pulsars
and companion star of GW events GW 190814 and GW 170817 from our model comply
with the estimated value of radius from observation.
| [
{
"created": "Wed, 20 Sep 2023 17:08:37 GMT",
"version": "v1"
}
] | 2023-09-21 | [
[
"Das",
"B.",
""
],
[
"Goswami",
"K. B.",
""
],
[
"Chattopadhyay",
"P. K.",
""
]
] | In this article a class of anisotropic compact star is analysed in Heintzmann geometry. We have introduced the pressure anisotropy parameter ($\alpha$) and solved Einstein field equations to obtain stellar model. We have considered $g_{tt}$ component as proposed by Heintzmann and by solving Einstein field equation, the $g_{rr}$ component is evaluated in presence of pressure anisotropy. It is noted that for isotropic star ($\alpha=0$), the maximum mass lies within the range $1.87-3.04~ M_{\odot}$ for radii ranges between $8-13$ Km. For anisotropic compact stars maximum mass increases with $\alpha$ and lies within the range $1.99-3.23~ M_{\odot}$ for anisotropy parameter $\alpha=0.5$. The physical viability of the model is examined by applying our model to study the properties of few known compact objects. It is noted that all the stability conditions are fulfilled in the proposed model. It is interesting to note that maximum mass calculated from our model and from solving TOV equation are approximately same and also the predicted radius of few newly observed pulsars and companion star of GW events GW 190814 and GW 170817 from our model comply with the estimated value of radius from observation. |
1011.4223 | Maria Babiuc | M.C. Babiuc, B. Szilagyi, J. Winicour, Y. Zlochower | A Characteristic Extraction Tool for Gravitational Waveforms | 30 pages, 15 figures, submitted to Physical Review D | Phys.Rev.D84:044057,2011 | 10.1103/PhysRevD.84.044057 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We develop and calibrate a characteristic waveform extraction tool whose
major improvements and corrections of prior versions allow satisfaction of the
accuracy standards required for advanced LIGO data analysis. The extraction
tool uses a characteristic evolution code to propagate numerical data on an
inner worldtube supplied by a 3+1 Cauchy evolution to obtain the gravitational
waveform at null infinity. With the new extraction tool, high accuracy and
convergence of the numerical error can be demonstrated for an inspiral and
merger of mass M binary black holes even for an extraction worldtube radius as
small as R = 20M. The tool provides a means for unambiguous comparison between
waveforms generated by evolution codes based upon different formulations of the
Einstein equations and based upon different numerical approximations.
| [
{
"created": "Thu, 18 Nov 2010 16:29:55 GMT",
"version": "v1"
},
{
"created": "Thu, 23 Jun 2011 21:37:26 GMT",
"version": "v2"
},
{
"created": "Mon, 8 Aug 2011 14:54:58 GMT",
"version": "v3"
}
] | 2011-09-26 | [
[
"Babiuc",
"M. C.",
""
],
[
"Szilagyi",
"B.",
""
],
[
"Winicour",
"J.",
""
],
[
"Zlochower",
"Y.",
""
]
] | We develop and calibrate a characteristic waveform extraction tool whose major improvements and corrections of prior versions allow satisfaction of the accuracy standards required for advanced LIGO data analysis. The extraction tool uses a characteristic evolution code to propagate numerical data on an inner worldtube supplied by a 3+1 Cauchy evolution to obtain the gravitational waveform at null infinity. With the new extraction tool, high accuracy and convergence of the numerical error can be demonstrated for an inspiral and merger of mass M binary black holes even for an extraction worldtube radius as small as R = 20M. The tool provides a means for unambiguous comparison between waveforms generated by evolution codes based upon different formulations of the Einstein equations and based upon different numerical approximations. |
gr-qc/0309097 | Stephane Fay | Stephane Fay | A reciprocal Wald theorem for varying gravitational function | 13 pages | Eur.Phys.J.C30d01:008,2003; Eur.Phys.J.C32S1:107-118,2004 | 10.1140/epjcd/s2003-01-008-2 | null | gr-qc | null | We study when a cosmological constant is a natural issue if it is mimicked by
the potential of a massive Hyperextended Scalar Tensor theory with a perfect
fluid for Bianchi type I and V models. We then deduce a reciprocal Wald theorem
giving the conditions such that the potential tends to a non vanishing constant
when the gravitational function varies. We also get the conditions allowing the
potentiel to vanish or diverge.
| [
{
"created": "Fri, 19 Sep 2003 13:00:47 GMT",
"version": "v1"
}
] | 2009-12-17 | [
[
"Fay",
"Stephane",
""
]
] | We study when a cosmological constant is a natural issue if it is mimicked by the potential of a massive Hyperextended Scalar Tensor theory with a perfect fluid for Bianchi type I and V models. We then deduce a reciprocal Wald theorem giving the conditions such that the potential tends to a non vanishing constant when the gravitational function varies. We also get the conditions allowing the potentiel to vanish or diverge. |
2309.08367 | Paul Tod | Paul Tod | Conformal Methods in Mathematical Cosmology | 14 pages, to appear in Phil.Trans.A; based on a talk at the Royal
Society Discussion Meeting "At the interface of asymptotics, conformal
methods and analysis in general relativity", London, 9th-10th May 2023 | null | null | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | When he first introduced the notion of a conformal boundary into the study of
asymptotically empty space-times, Penrose noted that that the boundary would be
null, space-like or time-like according as the cosmological constant $\Lambda$
was zero, positive or negative. While most applications of the idea of a
conformal boundary have been to the zero-$\Lambda$, asymptotically-Minkowskian
case, there also has been work on the nonzero cases. Here we review work with a
positive $\Lambda$, which is the appropriate case for cosmology of the universe
in which we live.
| [
{
"created": "Fri, 15 Sep 2023 12:48:23 GMT",
"version": "v1"
}
] | 2023-09-18 | [
[
"Tod",
"Paul",
""
]
] | When he first introduced the notion of a conformal boundary into the study of asymptotically empty space-times, Penrose noted that that the boundary would be null, space-like or time-like according as the cosmological constant $\Lambda$ was zero, positive or negative. While most applications of the idea of a conformal boundary have been to the zero-$\Lambda$, asymptotically-Minkowskian case, there also has been work on the nonzero cases. Here we review work with a positive $\Lambda$, which is the appropriate case for cosmology of the universe in which we live. |
2312.05260 | Carlos Alex Souza Da Silva Dr | Carlos Silva | A note on the AdS/CFT correspondence and the nature of spacetime in
quantum gravity | Published in: Nucl.Phys.B 998 (2024) 116402. Possible text overlap
with arxiv 2205.09502 [gr-qc] by the same author | Nucl.Phys.B 998 (2024) 116402 | 10.1016/j.nuclphysb.2023.116402 | null | gr-qc hep-th quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this paper, we address the nature of spacetime in quantum gravity in light
of a new version of the holographic principle that has established a
relationship between string theory and polymer holonomy structures similar to
Loop Quantum Cosmology spin networks. In front of the results found out, it is
possible to argue that, for such a relationship to work, spacetime must be seen
as emergent from a fundamental structure whose degrees of freedom correspond to
quantum correlations only.
| [
{
"created": "Fri, 1 Dec 2023 20:13:12 GMT",
"version": "v1"
}
] | 2023-12-12 | [
[
"Silva",
"Carlos",
""
]
] | In this paper, we address the nature of spacetime in quantum gravity in light of a new version of the holographic principle that has established a relationship between string theory and polymer holonomy structures similar to Loop Quantum Cosmology spin networks. In front of the results found out, it is possible to argue that, for such a relationship to work, spacetime must be seen as emergent from a fundamental structure whose degrees of freedom correspond to quantum correlations only. |
0709.0407 | Bahtiyar Ozgur Sarioglu | Ozgur Sarioglu, Bayram Tekin | Another proof of the positive energy theorem in gravity | v2: 7 pages, no figures, REVTeX4; Major revision including the change
in the title, the focus is now only on the D=4 case | null | null | null | gr-qc hep-th | null | We show that gravitational energy expression simplifies when a new set of
coordinates that satisfies a certain asymptotic gauge condition is used.
Compared to the ADM formula, positivity of the energy is more transparent in
this new construction. Our proof relies on the asymptotic symmetries
(specifically supertranslations) of the asymptotically flat spacetimes at
spatial infinity in four dimensions.
| [
{
"created": "Tue, 4 Sep 2007 12:24:33 GMT",
"version": "v1"
},
{
"created": "Thu, 14 Feb 2008 12:38:30 GMT",
"version": "v2"
}
] | 2008-02-14 | [
[
"Sarioglu",
"Ozgur",
""
],
[
"Tekin",
"Bayram",
""
]
] | We show that gravitational energy expression simplifies when a new set of coordinates that satisfies a certain asymptotic gauge condition is used. Compared to the ADM formula, positivity of the energy is more transparent in this new construction. Our proof relies on the asymptotic symmetries (specifically supertranslations) of the asymptotically flat spacetimes at spatial infinity in four dimensions. |
gr-qc/9806123 | Don Marolf | Donald Marolf | Spacetime Embedding Diagrams for Black Holes | 22 pages, 21 figures, RevTex. To be submitted to the American Journal
of Physics. Experts will wish only to skim appendix A and to look at the
pictures. Suggested Maple code is now compatible with MapleV4r5 | Gen.Rel.Grav. 31 (1999) 919-944 | 10.1023/A:1026646507201 | SU-GP-98/6-1 | gr-qc | null | We show that the 1+1 dimensional reduction (i.e., the radial plane) of the
Kruskal black hole can be embedded in 2+1 Minkowski spacetime and discuss how
features of this spacetime can be seen from the embedding diagram. The purpose
of this work is educational: The associated embedding diagrams may be useful
for explaining aspects of black holes to students who are familiar with special
relativity, but not general relativity.
| [
{
"created": "Tue, 30 Jun 1998 23:55:41 GMT",
"version": "v1"
},
{
"created": "Wed, 1 Jul 1998 00:02:00 GMT",
"version": "v2"
},
{
"created": "Wed, 8 Jul 1998 19:11:41 GMT",
"version": "v3"
}
] | 2015-06-25 | [
[
"Marolf",
"Donald",
""
]
] | We show that the 1+1 dimensional reduction (i.e., the radial plane) of the Kruskal black hole can be embedded in 2+1 Minkowski spacetime and discuss how features of this spacetime can be seen from the embedding diagram. The purpose of this work is educational: The associated embedding diagrams may be useful for explaining aspects of black holes to students who are familiar with special relativity, but not general relativity. |
2307.01343 | Yufeng Luo | Yufeng Luo, Qian Zhang, Roland Haas, Zachariah B. Etienne, Gabrielle
Allen | HPC-driven computational reproducibility in numerical relativity codes:
A use case study with IllinoisGRMHD | 23 pages, 6 figures, accepted to Classical and Quantum Gravity | null | 10.1088/1361-6382/ad13c5 | null | gr-qc cs.CE physics.comp-ph | http://creativecommons.org/licenses/by-nc-nd/4.0/ | Reproducibility of results is a cornerstone of the scientific method.
Scientific computing encounters two challenges when aiming for this goal.
Firstly, reproducibility should not depend on details of the runtime
environment, such as the compiler version or computing environment, so results
are verifiable by third-parties. Secondly, different versions of software code
executed in the same runtime environment should produce consistent numerical
results for physical quantities. In this manuscript, we test the feasibility of
reproducing scientific results obtained using the IllinoisGRMHD code that is
part of an open-source community software for simulation in relativistic
astrophysics, the Einstein Toolkit. We verify that numerical results of
simulating a single isolated neutron star with IllinoisGRMHD can be reproduced,
and compare them to results reported by the code authors in 2015. We use two
different supercomputers: Expanse at SDSC, and Stampede2 at TACC.
By compiling the source code archived along with the paper on both Expanse
and Stampede2, we find that IllinoisGRMHD reproduces results published in its
announcement paper up to errors comparable to round-off level changes in
initial data parameters. We also verify that a current version of
IlliinoisGRMHD reproduces these results once we account for bug fixes which has
occurred since the original publication
| [
{
"created": "Mon, 3 Jul 2023 20:28:48 GMT",
"version": "v1"
},
{
"created": "Fri, 8 Dec 2023 22:55:42 GMT",
"version": "v2"
}
] | 2023-12-12 | [
[
"Luo",
"Yufeng",
""
],
[
"Zhang",
"Qian",
""
],
[
"Haas",
"Roland",
""
],
[
"Etienne",
"Zachariah B.",
""
],
[
"Allen",
"Gabrielle",
""
]
] | Reproducibility of results is a cornerstone of the scientific method. Scientific computing encounters two challenges when aiming for this goal. Firstly, reproducibility should not depend on details of the runtime environment, such as the compiler version or computing environment, so results are verifiable by third-parties. Secondly, different versions of software code executed in the same runtime environment should produce consistent numerical results for physical quantities. In this manuscript, we test the feasibility of reproducing scientific results obtained using the IllinoisGRMHD code that is part of an open-source community software for simulation in relativistic astrophysics, the Einstein Toolkit. We verify that numerical results of simulating a single isolated neutron star with IllinoisGRMHD can be reproduced, and compare them to results reported by the code authors in 2015. We use two different supercomputers: Expanse at SDSC, and Stampede2 at TACC. By compiling the source code archived along with the paper on both Expanse and Stampede2, we find that IllinoisGRMHD reproduces results published in its announcement paper up to errors comparable to round-off level changes in initial data parameters. We also verify that a current version of IlliinoisGRMHD reproduces these results once we account for bug fixes which has occurred since the original publication |
2102.04744 | Jibitesh Dutta | Wompherdeiki Khyllep and Jibitesh Dutta | Cosmological dynamics and bifurcation analysis of the general
non-minimally coupled scalar field models | 17 pages and 14 figs | Eur. Phys. J. C 81, 774 (2021) | 10.1140/epjc/s10052-021-09559-x | null | gr-qc hep-ph hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Non-minimally coupled scalar field models are well-known for providing
interesting cosmological features. These include a late time dark energy
behavior, a phantom dark energy evolution without singularity, an early time
inflationary universe, scaling solutions, convergence to the standard
$\Lambda$CDM, etc. While the usual stability analysis helps us determine the
evolution of a model geometrically, bifurcation theory allows us to precisely
locate the parameters' values describing the global dynamics without a
fine-tuning of initial conditions. Using the center manifold theory and
bifurcation analysis, we show that the general model undergoes a transcritical
bifurcation, which predicts us to tune our models to have certain desired
dynamics. We obtained a class of models and a range of parameters capable of
describing a cosmic evolution from an early radiation era towards a late time
dark energy era over a wide range of initial conditions. There is also a
possible scenario of crossing the phantom divide line. We also find a class of
models where the late time attractor mechanism is indistinguishable from that
of a structurally stable general relativity based model; thus, we can elude the
big rip singularity generically. Therefore, bifurcation theory allows us to
select models that are viable with cosmological observations.
| [
{
"created": "Tue, 9 Feb 2021 10:18:05 GMT",
"version": "v1"
},
{
"created": "Thu, 2 Sep 2021 08:43:55 GMT",
"version": "v2"
}
] | 2021-09-03 | [
[
"Khyllep",
"Wompherdeiki",
""
],
[
"Dutta",
"Jibitesh",
""
]
] | Non-minimally coupled scalar field models are well-known for providing interesting cosmological features. These include a late time dark energy behavior, a phantom dark energy evolution without singularity, an early time inflationary universe, scaling solutions, convergence to the standard $\Lambda$CDM, etc. While the usual stability analysis helps us determine the evolution of a model geometrically, bifurcation theory allows us to precisely locate the parameters' values describing the global dynamics without a fine-tuning of initial conditions. Using the center manifold theory and bifurcation analysis, we show that the general model undergoes a transcritical bifurcation, which predicts us to tune our models to have certain desired dynamics. We obtained a class of models and a range of parameters capable of describing a cosmic evolution from an early radiation era towards a late time dark energy era over a wide range of initial conditions. There is also a possible scenario of crossing the phantom divide line. We also find a class of models where the late time attractor mechanism is indistinguishable from that of a structurally stable general relativity based model; thus, we can elude the big rip singularity generically. Therefore, bifurcation theory allows us to select models that are viable with cosmological observations. |
gr-qc/9801034 | Yousuke Itoh | T. Futamase, M. Hotta and Y. Itoh | Black Holes and Two-Dimensional Dilaton Gravity | 12 pages, LaTeX, Phys. Rev. D (in press) | Phys.Rev.D57:1129-1135,1998 | 10.1103/PhysRevD.57.1129 | TU-529 | gr-qc | null | We study the conditions for 2-dimensional dilaton gravity models to have
dynamical formation of black holes and construct all such models. Furthermore
we present a parametric representation of the general solutions of the black
holes.
| [
{
"created": "Mon, 12 Jan 1998 05:30:32 GMT",
"version": "v1"
}
] | 2014-11-17 | [
[
"Futamase",
"T.",
""
],
[
"Hotta",
"M.",
""
],
[
"Itoh",
"Y.",
""
]
] | We study the conditions for 2-dimensional dilaton gravity models to have dynamical formation of black holes and construct all such models. Furthermore we present a parametric representation of the general solutions of the black holes. |
1704.08116 | T. Damour | Thibault Damour and Philippe Spindel | Quantum Supersymmetric Cosmological Billiards and their Hidden Kac-Moody
Structure | 35 pages, 1 figure | Phys. Rev. D 95, 126011 (2017) | 10.1103/PhysRevD.95.126011 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study the quantum fermionic billiard defined by the dynamics of a
quantized supersymmetric squashed three-sphere (Bianchi IX cosmological model
within D=4 simple supergravity). The quantization of the homogeneous gravitino
field leads to a 64-dimensional fermionic Hilbert space. We focus on the 15-
and 20-dimensional subspaces (with fermion numbers N_F=2 and N_F=3) where there
exist propagating solutions of the supersymmetry constraints that carry (in the
small-wavelength limit) a chaotic spinorial dynamics generalizing the
Belinskii-Khalatnikov-Lifshitz classical "oscillatory" dynamics. By exactly
solving the supersymmetry constraints near each one of the three dominant
potential walls underlying the latter chaotic billiard dynamics, we compute the
three operators that describe the corresponding three potential-wall
reflections of the spinorial state describing, in supergravity, the quantum
evolution of the universe. It is remarkably found that the latter, purely
dynamically-defined, reflection operators satisfy generalized Coxeter relations
which define a type of spinorial extension of the Weyl group of the rank-3
hyperbolic Kac-Moody algebra AE_3.
| [
{
"created": "Wed, 26 Apr 2017 13:46:21 GMT",
"version": "v1"
}
] | 2017-07-05 | [
[
"Damour",
"Thibault",
""
],
[
"Spindel",
"Philippe",
""
]
] | We study the quantum fermionic billiard defined by the dynamics of a quantized supersymmetric squashed three-sphere (Bianchi IX cosmological model within D=4 simple supergravity). The quantization of the homogeneous gravitino field leads to a 64-dimensional fermionic Hilbert space. We focus on the 15- and 20-dimensional subspaces (with fermion numbers N_F=2 and N_F=3) where there exist propagating solutions of the supersymmetry constraints that carry (in the small-wavelength limit) a chaotic spinorial dynamics generalizing the Belinskii-Khalatnikov-Lifshitz classical "oscillatory" dynamics. By exactly solving the supersymmetry constraints near each one of the three dominant potential walls underlying the latter chaotic billiard dynamics, we compute the three operators that describe the corresponding three potential-wall reflections of the spinorial state describing, in supergravity, the quantum evolution of the universe. It is remarkably found that the latter, purely dynamically-defined, reflection operators satisfy generalized Coxeter relations which define a type of spinorial extension of the Weyl group of the rank-3 hyperbolic Kac-Moody algebra AE_3. |
1811.00385 | Javier Faba | Javier Faba Garc\'ia, Carlos Sab\'in | Dirac equation in exotic spacetimes | 7 pages, 3 figures | Phys. Rev. D 99, 025008 (2019) | 10.1103/PhysRevD.99.025008 | null | gr-qc quant-ph | http://creativecommons.org/licenses/by/4.0/ | We find solutions of the Dirac equation in curved spacetime. In particular,
we consider 1+1 dimensional sections of several exotic metrics: the Alcubierre
metric, which describes a scenario that allows faster-than-light (FTL)
velocity; the G\"odel metric, that describes a universe containing closed
timelike curves (CTC); and the Kerr metric, which corresponds to the spacetime
of a rotating black hole. Moreover, we also show that the techniques that we
use in these cases can be extended to nonstatic metrics.
| [
{
"created": "Tue, 30 Oct 2018 18:23:54 GMT",
"version": "v1"
},
{
"created": "Sun, 11 Nov 2018 15:09:09 GMT",
"version": "v2"
},
{
"created": "Tue, 15 Jan 2019 13:36:57 GMT",
"version": "v3"
}
] | 2019-01-16 | [
[
"García",
"Javier Faba",
""
],
[
"Sabín",
"Carlos",
""
]
] | We find solutions of the Dirac equation in curved spacetime. In particular, we consider 1+1 dimensional sections of several exotic metrics: the Alcubierre metric, which describes a scenario that allows faster-than-light (FTL) velocity; the G\"odel metric, that describes a universe containing closed timelike curves (CTC); and the Kerr metric, which corresponds to the spacetime of a rotating black hole. Moreover, we also show that the techniques that we use in these cases can be extended to nonstatic metrics. |
gr-qc/0104068 | Merced Montesinos | Merced Montesinos | Self-dual gravity with topological terms | LaTeX file, no figures, 8 pages. Accepted for publication in Class.
Quantum Grav | Class.Quant.Grav. 18 (2001) 1847-1852 | 10.1088/0264-9381/18/10/303 | null | gr-qc hep-th | null | The canonical analysis of the (anti-) self-dual action for gravity
supplemented with the (anti-) self-dual Pontrjagin term is carried out. The
effect of the topological term is to add a `magnetic' term to the original
momentum variable associated with the self-dual action leaving the Ashtekar
connection unmodified. In the new variables, the Gauss constraint retains its
form, while both vector and Hamiltonian constraints are modified. This shows,
the contribution of the Euler and Pontrjagin terms is not the same as that
coming from the term associated with the Barbero-Immirzi parameter, and thus
the analogy between the theta-angle in Yang-Mills theory and the
Barbero-Immirzi parameter of gravity is not appropriate.
| [
{
"created": "Mon, 23 Apr 2001 01:49:26 GMT",
"version": "v1"
}
] | 2009-11-07 | [
[
"Montesinos",
"Merced",
""
]
] | The canonical analysis of the (anti-) self-dual action for gravity supplemented with the (anti-) self-dual Pontrjagin term is carried out. The effect of the topological term is to add a `magnetic' term to the original momentum variable associated with the self-dual action leaving the Ashtekar connection unmodified. In the new variables, the Gauss constraint retains its form, while both vector and Hamiltonian constraints are modified. This shows, the contribution of the Euler and Pontrjagin terms is not the same as that coming from the term associated with the Barbero-Immirzi parameter, and thus the analogy between the theta-angle in Yang-Mills theory and the Barbero-Immirzi parameter of gravity is not appropriate. |
1108.3443 | Xin Li | Xin Li and Zhe Chang | Gravitational deflection of light in Rindler-type potential as a
possible resolution to the observations of Bullet Cluster 1E0657-558 | 11 pages | null | 10.1088/0253-6102/57/4/16 | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | The surface density $\Sigma$-map and the convergence $\kappa$-map of Bullet
Cluster 1E0657-558 show that the center of baryonic matters separates from the
center of gravitational force, and the distribution of gravitational force do
not possess spherical symmetry. This hints that a modified gravity with
difference to Newtonian inverse-square law at large scale, and less symmetry is
worth investigating. In this paper, we study the dynamics in Randers-Finsler
spacetime. The Newtonian limit and gravitational deflection of light in a
Rindler-type potential is focused in particular. It is shown that the
convergence in Finsler spacetime could account for the observations of Bullet
Cluster.
| [
{
"created": "Wed, 17 Aug 2011 10:48:33 GMT",
"version": "v1"
}
] | 2015-05-30 | [
[
"Li",
"Xin",
""
],
[
"Chang",
"Zhe",
""
]
] | The surface density $\Sigma$-map and the convergence $\kappa$-map of Bullet Cluster 1E0657-558 show that the center of baryonic matters separates from the center of gravitational force, and the distribution of gravitational force do not possess spherical symmetry. This hints that a modified gravity with difference to Newtonian inverse-square law at large scale, and less symmetry is worth investigating. In this paper, we study the dynamics in Randers-Finsler spacetime. The Newtonian limit and gravitational deflection of light in a Rindler-type potential is focused in particular. It is shown that the convergence in Finsler spacetime could account for the observations of Bullet Cluster. |
2104.00116 | Sebastian Schuster | Christian Pfeifer (Universit\"at Bremen) and Sebastian Schuster
(Univerzita Karlova) | Static spherically symmetric black holes in weak f(T)-gravity | v1: 20 pages, 5 figures; v2: 21 pages, 5 figures, no physics changes,
matches published version | Universe 2021, 7(5), 153 | 10.3390/universe7050153 | null | gr-qc | http://creativecommons.org/licenses/by/4.0/ | With the advent of gravitational wave astronomy and first pictures of the
"shadow" of the central black hole of our milky way, theoretical analyses of
black holes (and compact objects mimicking them sufficiently closely) have
become more important than ever. The near future promises more and more
detailed information about the observable black holes and black hole
candidates. This information could lead to important advances on constraints on
or evidence for modifications of general relativity. More precisely, we are
studying the influence of weak teleparallel perturbations on general
relativistic vacuum spacetime geometries in spherical symmetry. We find the
most general family of spherically symmetric, static vacuum solutions of the
theory, which are candidates for describing teleparallel black holes which
emerge as perturbations to the Schwarzschild black hole. We compare our
findings to results on black hole or static, spherically symmetric solutions in
teleparallel gravity discussed in the literature, by comparing the predictions
for classical observables such as the photon sphere, the perihelion shift, the
light deflection, and the Shapiro delay. On the basis of these observables, we
demonstrate that among the solutions we found, there exist spacetime geometries
that lead to much weaker bounds on teleparallel gravity than those found
earlier. Finally, we move on to a discussion of how the teleparallel
perturbations influence the Hawking evaporation in these spacetimes.
| [
{
"created": "Wed, 31 Mar 2021 21:03:00 GMT",
"version": "v1"
},
{
"created": "Thu, 20 May 2021 04:58:32 GMT",
"version": "v2"
}
] | 2021-05-21 | [
[
"Pfeifer",
"Christian",
"",
"Universität Bremen"
],
[
"Schuster",
"Sebastian",
"",
"Univerzita Karlova"
]
] | With the advent of gravitational wave astronomy and first pictures of the "shadow" of the central black hole of our milky way, theoretical analyses of black holes (and compact objects mimicking them sufficiently closely) have become more important than ever. The near future promises more and more detailed information about the observable black holes and black hole candidates. This information could lead to important advances on constraints on or evidence for modifications of general relativity. More precisely, we are studying the influence of weak teleparallel perturbations on general relativistic vacuum spacetime geometries in spherical symmetry. We find the most general family of spherically symmetric, static vacuum solutions of the theory, which are candidates for describing teleparallel black holes which emerge as perturbations to the Schwarzschild black hole. We compare our findings to results on black hole or static, spherically symmetric solutions in teleparallel gravity discussed in the literature, by comparing the predictions for classical observables such as the photon sphere, the perihelion shift, the light deflection, and the Shapiro delay. On the basis of these observables, we demonstrate that among the solutions we found, there exist spacetime geometries that lead to much weaker bounds on teleparallel gravity than those found earlier. Finally, we move on to a discussion of how the teleparallel perturbations influence the Hawking evaporation in these spacetimes. |
2403.12622 | Soumya Chakrabarti | Soumya Chakrabarti | Phase Transition and Thermodynamic Stability in an Entropy-driven
Universe | 10 pages, 6 figures, comments are welcome | null | null | null | gr-qc hep-th math-ph math.MP nlin.PS | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Motivated by the notion that the mathematics of gravity can be reproduced
from a statistical requirement of maximal entropy, we study the consequence of
introducing an entropic source term in the Einstein-Hilbert action. For a
spatially homogeneous cosmological system driven by this entropic source and
enveloped by a time evolving apparent horizon, we formulate a modified version
of the second law of thermodynamics. An explicit differential equation
governing the internal entropy profile is found. Using a Hessian matrix
analysis of the internal entropy we check the thermodynamic stability for a
{\Lambda}CDM cosmology, a unified cosmic expanson and a non-singular ekpyrotic
bounce. We find the mathematical condition for a second order phase transition
during these evolutions from the divergence of specific heat at constant
volume. The condition is purely kinematic and quadratic in nature, relating the
deceleration parameter and the jerk parameter that chalks out an interesting
curve on the parameter space. This condition is valid even without the entropic
source term and may be a general property of any phase transition.
| [
{
"created": "Tue, 19 Mar 2024 10:46:44 GMT",
"version": "v1"
}
] | 2024-03-20 | [
[
"Chakrabarti",
"Soumya",
""
]
] | Motivated by the notion that the mathematics of gravity can be reproduced from a statistical requirement of maximal entropy, we study the consequence of introducing an entropic source term in the Einstein-Hilbert action. For a spatially homogeneous cosmological system driven by this entropic source and enveloped by a time evolving apparent horizon, we formulate a modified version of the second law of thermodynamics. An explicit differential equation governing the internal entropy profile is found. Using a Hessian matrix analysis of the internal entropy we check the thermodynamic stability for a {\Lambda}CDM cosmology, a unified cosmic expanson and a non-singular ekpyrotic bounce. We find the mathematical condition for a second order phase transition during these evolutions from the divergence of specific heat at constant volume. The condition is purely kinematic and quadratic in nature, relating the deceleration parameter and the jerk parameter that chalks out an interesting curve on the parameter space. This condition is valid even without the entropic source term and may be a general property of any phase transition. |
gr-qc/0005042 | Leor Barack | Leor Barack | Self-force on a scalar particle in spherically-symmetric spacetime via
mode-sum regularization: radial trajectories | 28 pages, 2 eps figures. To be published in Phys. Rev. D | Phys.Rev.D62:084027,2000 | 10.1103/PhysRevD.62.084027 | null | gr-qc | null | Recently, we proposed a method for calculating the ``radiation reaction''
self-force exerted on a charged particle moving in a strong field orbit in a
black hole spacetime. In this approach, one first calculates the contribution
to the ``tail'' part of the self force due to each multipole mode of the
particle's self field. A certain analytic procedure is then applied to
regularize the (otherwise divergent) sum over modes. This involves the
derivation of certain regularization parameters using local analysis of the
(retarded) Green's function. In the present paper we present a detailed
formulation of this mode-sum regularization scheme for a scalar charge on a
class of static spherically-symmetric backgrounds (including, e.g., the
Schwarzschild, Reissner-Nordstr\"{o}m, and Schwarzschild-de Sitter spacetimes).
We fully implement the regularization scheme for an arbitrary radial trajectory
(not necessarily geodesic) by explicitly calculating all necessary
regularization parameters in this case.
| [
{
"created": "Fri, 12 May 2000 15:05:42 GMT",
"version": "v1"
},
{
"created": "Tue, 18 Jul 2000 17:04:16 GMT",
"version": "v2"
}
] | 2010-11-19 | [
[
"Barack",
"Leor",
""
]
] | Recently, we proposed a method for calculating the ``radiation reaction'' self-force exerted on a charged particle moving in a strong field orbit in a black hole spacetime. In this approach, one first calculates the contribution to the ``tail'' part of the self force due to each multipole mode of the particle's self field. A certain analytic procedure is then applied to regularize the (otherwise divergent) sum over modes. This involves the derivation of certain regularization parameters using local analysis of the (retarded) Green's function. In the present paper we present a detailed formulation of this mode-sum regularization scheme for a scalar charge on a class of static spherically-symmetric backgrounds (including, e.g., the Schwarzschild, Reissner-Nordstr\"{o}m, and Schwarzschild-de Sitter spacetimes). We fully implement the regularization scheme for an arbitrary radial trajectory (not necessarily geodesic) by explicitly calculating all necessary regularization parameters in this case. |
2408.07651 | Edgardo Franzin | Edgardo Franzin | Mini boson stars in higher dimensions are radially unstable | 7 pages, 4 figures; accepted in GRG | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Boson stars are self-gravitating solutions made entirely of fundamental
massive bosonic fields. Here we investigate mini boson stars in $D$ non-compact
spacetime dimensions and we show that they are dynamically unstable for $D>4$.
| [
{
"created": "Wed, 14 Aug 2024 16:26:20 GMT",
"version": "v1"
}
] | 2024-08-15 | [
[
"Franzin",
"Edgardo",
""
]
] | Boson stars are self-gravitating solutions made entirely of fundamental massive bosonic fields. Here we investigate mini boson stars in $D$ non-compact spacetime dimensions and we show that they are dynamically unstable for $D>4$. |
2103.08339 | Archana Dixit Dr. | Archana Dixit, Vinod Kumar Bharadwaj, Anirudh Pradhan | Barrow HDE model for Statefinder diagnostic in non-flat FRW universe | 19 pages, 21 figures | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this work we study a non-flat Friedmann-Robertson-Walker universe filled
with a pressure-less dark matter (DM) and Barrow holographic dark energy (BHDE)
whose IR cutoff is the apparent horizon. Among various DE models, (BHDE) model
shows the dynamical enthusiasm to discuss the universe's transition phase.
According to the new research, the universe transitioned smoothly from a
decelerated to an accelerated period of expansion in the recent past. We
exhibit that the development of $q$ relies upon the type of spatial curvature.
Here we study the equation of state (EoS) parameter for the BHDE model to
determine the cosmological evolution for the non-flat universe. The (EoS)
parameter and the deceleration parameter (DP) shows a satisfactory behaviour,
it does not cross the the phantom line. We also plot the statefinder diagram to
characterize the properties of the BHDE model by taking distinct values of
barrow exponent $\triangle$. Moreover, we likewise noticed the BHDE model in
the $(\omega_{D}-\omega_{D}^{'})$ plane, which can furnish us with a valuable,
powerful finding to the mathematical determination of the statefinder. In the
statefinder trajectory, this model was found to be able to reach the $\Lambda
CDM$ fixed point.
| [
{
"created": "Fri, 12 Mar 2021 10:47:09 GMT",
"version": "v1"
}
] | 2021-08-02 | [
[
"Dixit",
"Archana",
""
],
[
"Bharadwaj",
"Vinod Kumar",
""
],
[
"Pradhan",
"Anirudh",
""
]
] | In this work we study a non-flat Friedmann-Robertson-Walker universe filled with a pressure-less dark matter (DM) and Barrow holographic dark energy (BHDE) whose IR cutoff is the apparent horizon. Among various DE models, (BHDE) model shows the dynamical enthusiasm to discuss the universe's transition phase. According to the new research, the universe transitioned smoothly from a decelerated to an accelerated period of expansion in the recent past. We exhibit that the development of $q$ relies upon the type of spatial curvature. Here we study the equation of state (EoS) parameter for the BHDE model to determine the cosmological evolution for the non-flat universe. The (EoS) parameter and the deceleration parameter (DP) shows a satisfactory behaviour, it does not cross the the phantom line. We also plot the statefinder diagram to characterize the properties of the BHDE model by taking distinct values of barrow exponent $\triangle$. Moreover, we likewise noticed the BHDE model in the $(\omega_{D}-\omega_{D}^{'})$ plane, which can furnish us with a valuable, powerful finding to the mathematical determination of the statefinder. In the statefinder trajectory, this model was found to be able to reach the $\Lambda CDM$ fixed point. |
gr-qc/9511076 | null | B. L. Hu | Cosmology as `Condensed Matter' Physics | Latex 12 pages. Essay published in 1988 Conference Proceedings
reprinted here with no alteration. References current only up to July 1988 | null | null | umdpp 89-013 | gr-qc cond-mat | null | We note that in general there exist two basic aspects in any branch of
physics, including cosmology - one dealing with the attributes of basic
constituents and forces of nature, the other dealing with how structures arise
from them and how they evolve. Current research in quantum and superstring
cosmology is directed mainly towards the first aspect, even though a viable
theory of the underlying interactions is lacking. We call the attention to the
development of the second aspect, i.e., on the organization and processing of
the basic constituents of matter (in classical cosmology) and spacetime (in
quantum cosmology). Many newly developed concepts and techniques in condensed
matter physics stemming from the investigation of disordered, dynamical and
complex systems can guide us in asking the right questions and formulating new
solutions to existing and developing cosmological issues, thereby broadening
our view of the universe both in its formative and present state.
| [
{
"created": "Tue, 28 Nov 1995 05:41:39 GMT",
"version": "v1"
}
] | 2007-05-23 | [
[
"Hu",
"B. L.",
""
]
] | We note that in general there exist two basic aspects in any branch of physics, including cosmology - one dealing with the attributes of basic constituents and forces of nature, the other dealing with how structures arise from them and how they evolve. Current research in quantum and superstring cosmology is directed mainly towards the first aspect, even though a viable theory of the underlying interactions is lacking. We call the attention to the development of the second aspect, i.e., on the organization and processing of the basic constituents of matter (in classical cosmology) and spacetime (in quantum cosmology). Many newly developed concepts and techniques in condensed matter physics stemming from the investigation of disordered, dynamical and complex systems can guide us in asking the right questions and formulating new solutions to existing and developing cosmological issues, thereby broadening our view of the universe both in its formative and present state. |
1308.5770 | Kourosh Nozari | Kourosh Nozari, Faeze Kiani and Narges Rashidi | Gauss-Bonnet Braneworld Cosmology with Modified Induced Gravity on the
Brane | 22 pages, Accepted for publication in Adv. High Energy Phys | Adv. High Energy Phys. 2013 (2013) 968016, 12 | 10.1155/2013/968016 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We analyze the background cosmology for an extension of the DGP gravity with
Gauss-Bonnet term in the bulk and $f(R)$ gravity on the brane. We investigate
implications of this setup on the late-time cosmic history. Within a dynamical
system approach, we study cosmological dynamics of this setup focusing on the
role played by curvature effects. Finally we constraint the parameters of the
model by confrontation with recent observational data.
| [
{
"created": "Tue, 27 Aug 2013 07:06:06 GMT",
"version": "v1"
}
] | 2014-01-15 | [
[
"Nozari",
"Kourosh",
""
],
[
"Kiani",
"Faeze",
""
],
[
"Rashidi",
"Narges",
""
]
] | We analyze the background cosmology for an extension of the DGP gravity with Gauss-Bonnet term in the bulk and $f(R)$ gravity on the brane. We investigate implications of this setup on the late-time cosmic history. Within a dynamical system approach, we study cosmological dynamics of this setup focusing on the role played by curvature effects. Finally we constraint the parameters of the model by confrontation with recent observational data. |
1001.0949 | Joel Spruck | Joel Spruck (Johns Hopkins University), Yisong Yang (Polytechnic
Institute of New York University) | Charged cosmological dust solutions of the coupled Einstein and Maxwell
equations | null | null | null | null | gr-qc hep-th math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | It is well known through the work of Majumdar, Papapetrou, Hartle, and
Hawking that the coupled Einstein and Maxwell equations admit a static multiple
blackhole solution representing a balanced equilibrium state of finitely many
point charges. This is a result of the exact cancellation of gravitational
attraction and electric repulsion under an explicit condition on the mass and
charge ratio. The resulting system of particles, known as an extremely charged
dust, gives rise to examples of spacetimes with naked singularities. In this
paper, we consider the continuous limit of the
Majumdar--Papapetrou--Hartle--Hawking solution modeling a space occupied by an
extended distribution of extremely charged dust. We show that for a given
smooth distribution of matter of finite ADM mass there is a continuous family
of smooth solutions realizing asymptotically flat space metrics.
| [
{
"created": "Wed, 6 Jan 2010 18:50:29 GMT",
"version": "v1"
},
{
"created": "Thu, 28 Jan 2010 17:11:51 GMT",
"version": "v2"
}
] | 2010-01-28 | [
[
"Spruck",
"Joel",
"",
"Johns Hopkins University"
],
[
"Yang",
"Yisong",
"",
"Polytechnic\n Institute of New York University"
]
] | It is well known through the work of Majumdar, Papapetrou, Hartle, and Hawking that the coupled Einstein and Maxwell equations admit a static multiple blackhole solution representing a balanced equilibrium state of finitely many point charges. This is a result of the exact cancellation of gravitational attraction and electric repulsion under an explicit condition on the mass and charge ratio. The resulting system of particles, known as an extremely charged dust, gives rise to examples of spacetimes with naked singularities. In this paper, we consider the continuous limit of the Majumdar--Papapetrou--Hartle--Hawking solution modeling a space occupied by an extended distribution of extremely charged dust. We show that for a given smooth distribution of matter of finite ADM mass there is a continuous family of smooth solutions realizing asymptotically flat space metrics. |
2406.05458 | Fatemeh Sadeghi | Ali Derekeh, Behrouz Mirza, Pouya Heidari, Fatemeh Sadeghi, Reza
Bahani | A class of Taub-NUT metrics in the presence of a scalar field | null | null | null | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We derive a class of Taub-NUT metrics in the presence of a scalar field (TNS)
by applying the Ehlers transformation on the exact solutions that was recently
introduced in arXiv: 2307.09328 and arXiv: 2307.13588. Furthermore, we
investigate the effective potential, geodesics, topological charge, and
quasinormal modes (QNMs) for the obtained TNS metrics. We also use conformal
transformations to generate a new class of exact solutions of the
Einstein-conformal-scalar theory by using the obtained TNS solutions as seed
metrics. Finally we compare QNMs of the class of exact solutions.
| [
{
"created": "Sat, 8 Jun 2024 12:35:32 GMT",
"version": "v1"
}
] | 2024-06-11 | [
[
"Derekeh",
"Ali",
""
],
[
"Mirza",
"Behrouz",
""
],
[
"Heidari",
"Pouya",
""
],
[
"Sadeghi",
"Fatemeh",
""
],
[
"Bahani",
"Reza",
""
]
] | We derive a class of Taub-NUT metrics in the presence of a scalar field (TNS) by applying the Ehlers transformation on the exact solutions that was recently introduced in arXiv: 2307.09328 and arXiv: 2307.13588. Furthermore, we investigate the effective potential, geodesics, topological charge, and quasinormal modes (QNMs) for the obtained TNS metrics. We also use conformal transformations to generate a new class of exact solutions of the Einstein-conformal-scalar theory by using the obtained TNS solutions as seed metrics. Finally we compare QNMs of the class of exact solutions. |
0805.1972 | John T. Whelan | John T. Whelan, Reinhard Prix, and Deepak Khurana | Improved search for galactic white dwarf binaries in Mock LISA Data
Challenge 1B using an F-statistic template bank | 11 pages, 4 included figures, submitted to Classical and Quantum
Gravity for GWDAW12 proceedings | null | 10.1088/0264-9381/25/18/184029 | LIGO-P080037-00-Z | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We report on our F-statistic search for white-dwarf binary signals in the
Mock LISA Data Challenge 1B (MLDC1B). We focus in particular on the
improvements in our search pipeline since MLDC1, namely refinements in the
search pipeline and the use of a more accurate detector response (rigid
adiabatic approximation). The search method employs a hierarchical
template-grid based exploration of the parameter space, using a coincidence
step to distinguish between primary (``true'') and secondary maxima, followed
by a final (multi-TDI) ``zoom'' stage to provide an accurate parameter
estimation of the final candidates.
| [
{
"created": "Wed, 14 May 2008 06:00:16 GMT",
"version": "v1"
},
{
"created": "Fri, 27 Jun 2008 14:06:27 GMT",
"version": "v2"
}
] | 2009-11-13 | [
[
"Whelan",
"John T.",
""
],
[
"Prix",
"Reinhard",
""
],
[
"Khurana",
"Deepak",
""
]
] | We report on our F-statistic search for white-dwarf binary signals in the Mock LISA Data Challenge 1B (MLDC1B). We focus in particular on the improvements in our search pipeline since MLDC1, namely refinements in the search pipeline and the use of a more accurate detector response (rigid adiabatic approximation). The search method employs a hierarchical template-grid based exploration of the parameter space, using a coincidence step to distinguish between primary (``true'') and secondary maxima, followed by a final (multi-TDI) ``zoom'' stage to provide an accurate parameter estimation of the final candidates. |
1508.04677 | Bijan Saha Dr. | Bijan Saha and Victor S. Rikhvitsky | Nonlinear Spinor Fields in LRS Bianchi type-I spacetime: Theory and
observation | 10 pages 7 figures. arXiv admin note: text overlap with
arXiv:1507.06236 | Gravitation and Cosmology, Vol. 23, PP. 329 - 336, 2017 | 10.1134/S0202289317040193 | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Within the scope of a LRS Bianchi type-I cosmological model we study the role
of the nonlinear spinor field in the evolution of the Universe. In doing so we
consider a polynomial type of nonlinearity that describes different stages of
the evolution. Finally we also use the observational data to fix the problem
parameters that match best with the real picture of the evolution. The
assessment of the age of the Universe in case of the soft beginning of
expansion (initial speed of expansion in a point of singularity is equal to
zero) the age was found 15 billion years, whereas in case of the hard beginning
(nontrivial initial speed) it was found that the Universe is 13.7 billion years
old.
| [
{
"created": "Wed, 19 Aug 2015 15:17:29 GMT",
"version": "v1"
}
] | 2017-11-02 | [
[
"Saha",
"Bijan",
""
],
[
"Rikhvitsky",
"Victor S.",
""
]
] | Within the scope of a LRS Bianchi type-I cosmological model we study the role of the nonlinear spinor field in the evolution of the Universe. In doing so we consider a polynomial type of nonlinearity that describes different stages of the evolution. Finally we also use the observational data to fix the problem parameters that match best with the real picture of the evolution. The assessment of the age of the Universe in case of the soft beginning of expansion (initial speed of expansion in a point of singularity is equal to zero) the age was found 15 billion years, whereas in case of the hard beginning (nontrivial initial speed) it was found that the Universe is 13.7 billion years old. |
2107.04889 | Reinaldo Gleiser | Reinaldo J. Gleiser | The Linet-Tian metrics are a restricted set of Krasi\'nski's solutions
of Einstein's field equations for a rotating perfect fluid | 7 pages, No figures | null | 10.1088/1361-6382/ac33be | null | gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In this note we show that the Linet-Tian family of solutions of the vacuum
Einstein equations with a cosmological constant are a restricted set of the
solutions of the Einstein field equations for a rotating perfect fluid
previously found by A. Krasi\'nski.
| [
{
"created": "Sat, 10 Jul 2021 18:52:15 GMT",
"version": "v1"
}
] | 2021-12-08 | [
[
"Gleiser",
"Reinaldo J.",
""
]
] | In this note we show that the Linet-Tian family of solutions of the vacuum Einstein equations with a cosmological constant are a restricted set of the solutions of the Einstein field equations for a rotating perfect fluid previously found by A. Krasi\'nski. |
0904.3577 | Shintaro Sawayama | Shintaro Sawayama | Solving the Wheeler-DeWitt of Small Universe | 6 page, no figure | null | null | null | gr-qc | http://creativecommons.org/licenses/by/3.0/ | We can solve the Wheeler-DeWitt equation of the small universe enough to
metric becomes diagonal and take a Gaussian normal coordinate. Our previous
works are concerning to this paper. In this paper, we only write how to solve
the Wheeler-DeWitt equation of such universe. Our motivation is simple, that is
to solve the Wheeler-DeWitt equation. Even if the Wheeler-DeWitt equation is
solved, quantum gravity does not complete yet. However, this work may be one of
the first step to quantum gravity.
| [
{
"created": "Thu, 23 Apr 2009 00:04:12 GMT",
"version": "v1"
}
] | 2009-04-24 | [
[
"Sawayama",
"Shintaro",
""
]
] | We can solve the Wheeler-DeWitt equation of the small universe enough to metric becomes diagonal and take a Gaussian normal coordinate. Our previous works are concerning to this paper. In this paper, we only write how to solve the Wheeler-DeWitt equation of such universe. Our motivation is simple, that is to solve the Wheeler-DeWitt equation. Even if the Wheeler-DeWitt equation is solved, quantum gravity does not complete yet. However, this work may be one of the first step to quantum gravity. |
2008.04805 | Marek Li\v{s}ka | Ana Alonso-Serrano and Marek Li\v{s}ka | New perspective on thermodynamics of spacetime: The emergence of
unimodular gravity and the equivalence of entropies | 19 pages, 1 figure Version accepted in PRD. Few typos corrected and
some references added | Phys. Rev. D 102, 104056 (2020) | 10.1103/PhysRevD.102.104056 | null | gr-qc hep-th | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a novel derivation of Einstein equations from the balance between
Clausius entropy crossing the boundary of a local causal diamond and
entanglement entropy associated with its horizon. Comparing this derivation
with the entanglement equilibrium approach developed by Jacobson, we are able
to argue for the equivalence of matter entanglement and Clausius entropy in the
semiclassical regime. We also provide a direct comparison of both entropies for
conformal matter, showing their equivalence without appealing to gravitational
dynamics. Furthermore, we determine that gravitational dynamics implied by
thermodynamics of spacetime, in fact, corresponds to unimodular gravity rather
than general relativity.
| [
{
"created": "Tue, 11 Aug 2020 16:01:21 GMT",
"version": "v1"
},
{
"created": "Mon, 16 Nov 2020 12:16:12 GMT",
"version": "v2"
}
] | 2020-11-25 | [
[
"Alonso-Serrano",
"Ana",
""
],
[
"Liška",
"Marek",
""
]
] | We present a novel derivation of Einstein equations from the balance between Clausius entropy crossing the boundary of a local causal diamond and entanglement entropy associated with its horizon. Comparing this derivation with the entanglement equilibrium approach developed by Jacobson, we are able to argue for the equivalence of matter entanglement and Clausius entropy in the semiclassical regime. We also provide a direct comparison of both entropies for conformal matter, showing their equivalence without appealing to gravitational dynamics. Furthermore, we determine that gravitational dynamics implied by thermodynamics of spacetime, in fact, corresponds to unimodular gravity rather than general relativity. |
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